document cycles, stack rows, etc terminology

[Qyriad]

The docs refer to instructions and stdlib procedures as taking some number of "cycles", for example the following procedure is documented to take 4+11+4 = 19 cycles:

begin
    push.5.0
    push.6.0
    exec.u64::lt
    dropw
end

but miden-vm run and miden-vm analyze reports "VM cycles: 41 extended to 64 steps (35% padding), and "Stack rows: 30". In a conversation with @plafer I was told that "stack rows" are what the documentation is calling "cycles" for purposes of instructions and procedures. And also that you may get more rows if there are relatively few, but heavy, instructions, and that to get the number I actually want, I should look at the per-instruction cycle counts given by miden-vm analyze`.

The docs could use an explanation for why the above example reports "41 cycles", "30 stack rows", "39 range checker rows", etc.

[bobbinth]

For simple procedures like this, we can count cycles by hand. For example:

begin
    push.5.0      # 2 cycles
    push.6.0      # 2 cycles
    exec.u64::lt  # 11 cycles
    dropw         # 4 cycles
end

So, executing this procedure should take 19 cycles.

For larger procedures we could use "stack rows" from miden-vm analyze command as various overheads won't make too much difference there.