[issue40275] test.support has way too many imports

[hai shi]

hai shi <shihai1991 at 126.com> added the comment:

> These three PRs combined reduce the number of imported modules from 179 to 105 (not including 24 modules imported by the bare interpreter) and reduce the hot import time from 160 ms to 80 ms.

Good job, serhiy. I tested your patches in my vm, the number of importing module have been reduced. Could you paste your performance benchmark test? I got a no siginificant change :( when I run: 
$ ./python -m pyperf timeit --compare-to python3.9 "from test import support" -p 100
python3.9: ..................................................................................................... 820 ns +- 206 ns

python: ..................................................................................................... 809 ns +- 201 ns

Mean +- std dev: [python3.9] 820 ns +- 206 ns -> [python] 809 ns +- 201 ns: 1.01x faster (-1%)
Not significant!

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<https://bugs.python.org/issue40275>
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