Add durations to unittest in 3.12

[sobolevn]

Source commit: python/cpython@6883007

[srittau]

At least collectedDurations (ugh, camel case...) uses list[tuple[str, float]]:

https://github.com/python/cpython/blob/24b9bdd6eaf0b04667b6cd4c8154f7c7c10c2398/Lib/unittest/result.py#L170

[srittau]

Although the docs are wrong: https://docs.python.org/3.12/library/unittest.html?highlight=collecteddurations#unittest.TestResult.collectedDurations

But even the tests use str: https://github.com/python/cpython/blob/24b9bdd6eaf0b04667b6cd4c8154f7c7c10c2398/Lib/test/test_unittest/test_runner.py#L1402

I will send a PR to CPython.

[sobolevn]

Yeap, I used docs for this type. Let's wait for your PR to land first.

[srittau]

Looks like a deliberate change to fix a circular reference, they just forgot to update the docs: python/cpython#106888

[srittau]

Thanks!

[AlexWaygood]

Thanks!

[github-actions]

Diff from mypy_primer, showing the effect of this PR on open source code:

tornado (https://github.com/tornadoweb/tornado)
+ tornado/test/runtests.py:72: error: Unused "type: ignore" comment  [unused-ignore]
+ tornado/test/runtests.py:78: error: Unused "type: ignore" comment  [unused-ignore]