Baremetal multicore support

[aykevl]

Use multiple cores of the "baremetal" riscv-qemu target. The goal is to iron out all the bugs on an easy-to-debug target before moving on to more interesting targets like RP2040. After this PR is done, the RP2040 should be relatively easy to add support for (since I already wrote most of that code).

Work in progress. This already mostly works, but there are a few things that still need to be fixed:

• There's a timing bug where if one goroutine pauses, and another already running goroutine pauses for a shorter time, the second may not be woken up at the earlier time. fixed!
• Timers (time.NewTimer etc) need to be implemented.
• Stack scanning (for the GC) needs to be implemented.

[github-actions]

Size difference with the dev branch:

Binary size difference

drivers/sizes-dev.txt has more commands than drivers/sizes-pr.txt
    tinygo build -size short -o ./build/test.hex -target=arduino ./examples/servo
 flash                          ram
 before   after   diff          before   after   diff
  16584   16584      0   0.00%    4172    4172      0   0.00% tinygo build -size short -o ./build/test.hex -target=feather-rp2040 ./examples/adafruit4650
  61852   61852      0   0.00%    6180    6180      0   0.00% tinygo build -size short -o ./build/test.hex -target=itsybitsy-m0 ./examples/adt7410/main.go
   8844    8844      0   0.00%    4748    4748      0   0.00% tinygo build -size short -o ./build/test.hex -target=itsybitsy-m0 ./examples/adxl345/main.go
  13576   13576      0   0.00%    6796    6796      0   0.00% tinygo build -size short -o ./build/test.hex -target=pybadge ./examples/amg88xx
   9004    9004      0   0.00%    4748    4748      0   0.00% tinygo build -size short -o ./build/test.hex -target=itsybitsy-m0 ./examples/apa102/main.go
  11820   11820      0   0.00%    6580    6580      0   0.00% tinygo build -size short -o ./build/test.hex -target=nano-33-ble ./examples/apds9960/proximity/main.go
   9268    9268      0   0.00%    4752    4752      0   0.00% tinygo build -size short -o ./build/test.hex -target=itsybitsy-m0 ./examples/apa102/itsybitsy-m0/main.go
   7580    7580      0   0.00%    2320    2320      0   0.00% tinygo build -size short -o ./build/test.hex -target=microbit ./examples/at24cx/main.go
   8088    8088      0   0.00%    4740    4740      0   0.00% tinygo build -size short -o ./build/test.hex -target=itsybitsy-m0 ./examples/bh1750/main.go
   7456    7456      0   0.00%    4740    4740      0   0.00% tinygo build -size short -o ./build/test.hex -target=itsybitsy-m0 ./examples/blinkm/main.go
  71132   71132      0   0.00%    3656    3656      0   0.00% tinygo build -size short -o ./build/test.hex -target=pinetime     ./examples/bma42x/main.go
  64556   64556      0   0.00%    6196    6196      0   0.00% tinygo build -size short -o ./build/test.hex -target=itsybitsy-m0 ./examples/bmi160/main.go
  27628   27628      0   0.00%    4780    4780      0   0.00% tinygo build -size short -o ./build/test.hex -target=itsybitsy-m0 ./examples/bmp180/main.go
  64480   64480      0   0.00%    6220    6220      0   0.00% tinygo build -size short -o ./build/test.hex -target=itsybitsy-m0 ./examples/bmp280/main.go
  11948   11948      0   0.00%    4812    4812      0   0.00% tinygo build -size short -o ./build/test.hex -target=trinket-m0 ./examples/bmp388/main.go
   7872    7872      0   0.00%    3352    3352      0   0.00% tinygo build -size short -o ./build/test.hex -target=bluepill ./examples/ds1307/sram/main.go
  22188   22188      0   0.00%    3556    3556      0   0.00% tinygo build -size short -o ./build/test.hex -target=bluepill ./examples/ds1307/time/main.go
  70144   70144      0   0.00%    6368    6368      0   0.00% tinygo build -size short -o ./build/test.hex -target=itsybitsy-m0 ./examples/ds3231/main.go
   4632    4632      0   0.00%    2280    2280      0   0.00% tinygo build -size short -o ./build/test.hex -target=microbit ./examples/easystepper/main.go
  70328   70328      0   0.00%    6980    6980      0   0.00% tinygo build -size short -o ./build/test.hex -target=itsybitsy-m0 ./examples/flash/console/spi
  67088   67088      0   0.00%    9020    9020      0   0.00% tinygo build -size short -o ./build/test.hex -target=pyportal ./examples/flash/console/qspi
   7304    7304      0   0.00%    2284    2284      0   0.00% tinygo build -size short -o ./build/test.hex -target=microbit ./examples/gc9a01/main.go
  67496   67496      0   0.00%    6360    6360      0   0.00% tinygo build -size short -o ./build/test.hex -target=feather-m0 ./examples/gps/i2c/main.go
  67912   67912      0   0.00%    6504    6504      0   0.00% tinygo build -size short -o ./build/test.hex -target=feather-m0 ./examples/gps/uart/main.go
   7868    7868      0   0.00%    4740    4740      0   0.00% tinygo build -size short -o ./build/test.hex -target=itsybitsy-m0 ./examples/hcsr04/main.go
   5760    5760      0   0.00%    2280    2280      0   0.00% tinygo build -size short -o ./build/test.hex -target=microbit ./examples/hd44780/customchar/main.go
   5800    5800      0   0.00%    2280    2280      0   0.00% tinygo build -size short -o ./build/test.hex -target=microbit ./examples/hd44780/text/main.go
  10424   10424      0   0.00%    4748    4748      0   0.00% tinygo build -size short -o ./build/test.hex -target=arduino-nano33 ./examples/hd44780i2c/main.go
  14704   14704      0   0.00%    6580    6580      0   0.00% tinygo build -size short -o ./build/test.hex -target=nano-33-ble ./examples/hts221/main.go
  16180   16180      0   0.00%    2364    2364      0   0.00% tinygo build -size short -o ./build/test.hex -target=microbit ./examples/hub75/main.go
  10276   10276      0   0.00%    6916    6916      0   0.00% tinygo build -size short -o ./build/test.hex -target=pyportal ./examples/ili9341/basic
  11064   11064      0   0.00%    4876    4876      0   0.00% tinygo build -size short -o ./build/test.hex -target=xiao ./examples/ili9341/basic
  29640   29640      0   0.00%   38076   38076      0   0.00% tinygo build -size short -o ./build/test.hex -target=pyportal ./examples/ili9341/pyportal_boing
  10304   10304      0   0.00%    6916    6916      0   0.00% tinygo build -size short -o ./build/test.hex -target=pyportal ./examples/ili9341/scroll
  11144   11144      0   0.00%    4876    4876      0   0.00% tinygo build -size short -o ./build/test.hex -target=xiao ./examples/ili9341/scroll
 263728  263728      0   0.00%   46744   46744      0   0.00% tinygo build -size short -o ./build/test.hex -target=pyportal ./examples/ili9341/slideshow
  11048   11048      0   0.00%    4780    4780      0   0.00% tinygo build -size short -o ./build/test.hex -target=circuitplay-express ./examples/lis3dh/main.go
  14060   14060      0   0.00%    6580    6580      0   0.00% tinygo build -size short -o ./build/test.hex -target=nano-33-ble ./examples/lps22hb/main.go
  26356   26356      0   0.00%    2328    2328      0   0.00% tinygo build -size short -o ./build/test.hex -target=microbit ./examples/lsm303agr/main.go
  12372   12372      0   0.00%    4788    4788      0   0.00% tinygo build -size short -o ./build/test.hex -target=arduino-nano33 ./examples/lsm6ds3/main.go
  10084   10084      0   0.00%    4740    4740      0   0.00% tinygo build -size short -o ./build/test.hex -target=itsybitsy-m0 ./examples/mag3110/main.go
   9244    9244      0   0.00%    4772    4772      0   0.00% tinygo build -size short -o ./build/test.hex -target=itsybitsy-m0 ./examples/mcp23017/main.go
   9648    9648      0   0.00%    4780    4780      0   0.00% tinygo build -size short -o ./build/test.hex -target=itsybitsy-m0 ./examples/mcp23017-multiple/main.go
   9492    9492      0   0.00%    4748    4748      0   0.00% tinygo build -size short -o ./build/test.hex -target=itsybitsy-m0 ./examples/mcp3008/main.go
  69228   69228      0   0.00%    6196    6196      0   0.00% tinygo build -size short -o ./build/test.hex -target=itsybitsy-m0 ./examples/mcp2515/main.go
   7544    7544      0   0.00%    4748    4748      0   0.00% tinygo build -size short -o ./build/test.hex -target=itsybitsy-m0 ./examples/mma8653/main.go
   7452    7452      0   0.00%    4740    4740      0   0.00% tinygo build -size short -o ./build/test.hex -target=itsybitsy-m0 ./examples/mpu6050/main.go
  75832   75832      0   0.00%    7452    7452      0   0.00% tinygo build -size short -o ./build/test.hex -target=p1am-100 ./examples/p1am/main.go
  12212   12212      0   0.00%    3352    3352      0   0.00% tinygo build -size short -o ./build/test.hex -target=pico ./examples/pca9685/main.go
   6272    6272      0   0.00%    3292    3292      0   0.00% tinygo build -size short -o ./build/test.hex -target=microbit ./examples/pcd8544/setbuffer/main.go
   4656    4656      0   0.00%    2284    2284      0   0.00% tinygo build -size short -o ./build/test.hex -target=microbit ./examples/pcd8544/setpixel/main.go
  10500   10500      0   0.00%    3328    3328      0   0.00% tinygo build -size short -o ./build/test.hex -target=feather-rp2040 ./examples/seesaw
  27132   27148     16   0.06%    3640    3640      0   0.00% tinygo build -size short -o ./build/test.hex -target=microbit ./examples/microbitmatrix/main.go
  26948   26972     24   0.09%    5620    5620      0   0.00% tinygo build -size short -o ./build/test.hex -target=microbit-v2 ./examples/microbitmatrix/main.go
1525752 1525792     40   0.00%  335708  335708      0   0.00%

[aykevl]

Rebased and fixed one of the 3 issues listed above.

[aykevl]

Implemented support for timers.