gh-82054: Implements test.regrtest unittest sharding to pull in long tails for asyncio

[zitterbewegung]

gh-82054: Implements test.regrtest unittest sharding to pull in long tails for asyncio and compiler

TLDR: This runs test_asyncio and test_compiler sub-tests in parallel

Below is a summary about this change which is the same information from the issue in cinder that addressed this. It can be found at facebookincubator/cinder@3c6be01

Summary:

These two tests are typically the long-poles in runs because they are modules with a lot of further sub-tests run serially. By breaking out the sub-tests as independent modules we can run a lot more in parallel.

The real win comes in the next diff but with this change alone on my devserver:

• With a debug build:
  • time make testcinder goes from ~25m -> ~19m.
  • time make testcinder_jit goes from ~26m -> ~18m.
• With a release build:
  • time make testcinder goes from ~6m15s -> ~4m45s.
  • time make testcinder_jit goes from ~6m -> ~5m30s.

While this is a bit hacky and annoyingly involves changing CPython test infra, I think the maintenance overhead is worth it. It's not a complicated change and I think the win in productivity with the diff above is significant.

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[zitterbewegung]

Committed on wrong git account.