generate test coverage+results in a monorepo-friendly way

[matt-codecov]

needed for https://github.com/codecov/umbrella/pull/17

currently the docker image is built and coverage data is generated as if worker is its own repo and all the files are in the repo root. in umbrella that is no longer true - worker exists in apps/worker/ and we want that prefix to be applied to every source file we have data for

this PR sets up shared in /app/apps/worker instead of /app inside the docker container

• for PRs in worker, path fixing strips those extra directories off the path and nothing is different (see this PR's indirect changes for example - if paths were not the same we would see a bunch of "No data" entries)
• for PRs in umbrella, path fixing will strip /app but apps/worker will remain like we want (see https://github.com/codecov/umbrella/pull/17 for example)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.25%. Comparing base (899d4dd) to head (ab83759).
Report is 1 commits behind head on main.

✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1105   +/-   ##
=======================================
  Coverage   97.25%   97.25%           
=======================================
  Files         454      454           
  Lines       37447    37447           
=======================================
  Hits        36418    36418           
  Misses       1029     1029           

Flag	Coverage Δ
integration	43.06% <ø> (ø)
unit	89.81% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[codecov-notifications]

Codecov Report

All modified and coverable lines are covered by tests ✅

✅ All tests successful. No failed tests found.

📢 Thoughts on this report? Let us know!