Add flaky pytest infrastructure and weekend runners

[paul0403]

Context:
We wish to reduce flaky tests in CI.
There is a python package flaky (which we already have in our requirements.txt) that reruns failed tests to hunt for flakiness.
Let's actually use it.

Description of the Change:

• Add flaky infrastructure. A pytest run that hunts for flaky tests can be launched by make pytest ENABLE_FLAKY=ON
• 4 tests that change some global state cannot be run more than once. We force them to be run only once. None of them are of a stochastic nature
• Add a script to launch flaky hunting runs on weekends.

Benefits:
If any new tests are flaky, this weekend runner will catch them!

[sc-87028]

[github-actions]

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[dime10]

Great idea 💯

The only thing I would say is that we should fix those global state mutations instead of forcing the tests to only run once :)

[paul0403]

Since this action installs from testpypi, this PR's CI will fail tests for tests depending on new features still not on testpypi yet. For example, Tuesday midnight's test pypi will fail tests added on Wednesday.

This is fine. I only enable the script on PRs to check the script itself.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.61%. Comparing base (2c0917c) to head (86755fb).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1799   +/-   ##
=======================================
  Coverage   96.61%   96.61%           
=======================================
  Files          82       82           
  Lines        9265     9265           
  Branches      875      875           
=======================================
  Hits         8951     8951           
  Misses        255      255           
  Partials       59       59           

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[paul0403]

This one is more straightforward, this Failing class uses a class variable to keep track of labels it already saw, and this track record of labels is not reset over different tests, or different runs of the same test.

I just add a fixture to reset it everytime.