Rearragne directory structure and update symbol visibility #41

Job	Run time
Build wheels on macos-13-xlarge	7m 15s
Build wheels on ubuntu-20.04	17m 6s
Build wheels on macos-13-xlarge	6m 58s
Build wheels on ubuntu-20.04	16m 50s
Build wheels on macos-13-xlarge	6m 51s
Build wheels on ubuntu-20.04	17m 42s
Build wheels on ubuntu-20.04	17m 17s
Build wheels on macos-12	24m 7s
Build wheels on macos-12	19m 12s
Build wheels on macos-12	18m 16s
Build wheels on macos-12	15m 33s
Build wheels on windows-latest	22m 58s
Build wheels on windows-latest	23m 4s
Build wheels on windows-latest	22m 53s
Build wheels on windows-latest	22m 36s
	4h 18m 38s

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