emit junit results in a monorepo-friendly way

[matt-codecov]

see resulting test file paths here: https://app.codecov.io/gh/codecov/codecov-api/tests/matt%2Fmonorepo-friendly-junit

sort by "Last run" to get the results of the most recent attempt

this is a bit of a hack, but better solutions are all way, way easier after cutover and involve more invasive changes to how things work.

the worker/shared/api PRs pass --rootdir=${PYTEST_ROOTDIR} -c pytest.ini to pytest invocations. --rootdir=${PYTEST_ROOTDIR} allows us to override the rootdir, and -c pytest.ini makes sure pytest can still find its config when we do.

by default, the rootdir is ., which is the directory pytest.ini lives in. it's as if neither argument were passed at all. the original worker/api/shared repos use the default, so they are unchanged.

the gha-workflows PR adds an optional input to the test workflows which allow PYTEST_ROOTDIR to be overridden. umbrella passes in /app, and the result is that test file paths inside junit.xml will have the prefix umbrella wants (e.g. apps/worker for worker).

so, the original repositories generate junit files with test file paths relative to the repo root, just like always. and umbrella will generate junit files with test file paths relative to umbrella's root, which is what umbrella wants.

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.31%. Comparing base (8b67765) to head (9320511).
Report is 1 commits behind head on main.

✅ All tests successful. No failed tests found.

Additional details and impacted files

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  Coverage   96.31%   96.31%           
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  Files         492      492           
  Lines       16805    16805           
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  Hits        16185    16185           
  Misses        620      620           

Flag	Coverage Δ
unit	96.31% <ø> (ø)

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[codecov-notifications]

Codecov Report

All modified and coverable lines are covered by tests ✅

✅ All tests successful. No failed tests found.

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