ref: replace pytest-rerunfailures with flaky

[asottile-sentry]

pytest-rerunfailures does not run class teardowns in pytest 8.2+

see pytest-dev/pytest#11833

[github-actions]

🚨 Warning: This pull request contains Frontend and Backend changes!

It's discouraged to make changes to Sentry's Frontend and Backend in a single pull request. The Frontend and Backend are not atomically deployed. If the changes are interdependent of each other, they must be separated into two pull requests and be made forward or backwards compatible, such that the Backend or Frontend can be safely deployed independently.

Have questions? Please ask in the #discuss-dev-infra channel.

[codecov]

❌ 5 Tests Failed:

Tests completed	Failed	Passed	Skipped
21746	5	21741	208

View the top 3 failed tests by shortest run time

tests.acceptance.test_sidebar.SidebarTest test_new_sidebar

Stack Traces | 5.22s run time

No failure message available

tests.snuba.sessions.test_sessions_v2 test_massage_unbalanced_results

Stack Traces | 5.34s run time

No failure message available

tests.acceptance.test_shared_issue.SharedIssueTest test_python_event

Stack Traces | 11.8s run time

No failure message available

To view individual test run time comparison to the main branch, go to the Test Analytics Dashboard

[getsantry]

This pull request has gone three weeks without activity. In another week, I will close it.

But! If you comment or otherwise update it, I will reset the clock, and if you add the label WIP, I will leave it alone unless WIP is removed ... forever!

---

"A weed is but an unloved flower." ― Ella Wheeler Wilcox 🥀