Better CI setup

[solnic]

This adds a new top-level workflow called "Tests & CodeCov" that orchestrates running tests for all 6 gems and once they are done, it runs CodeCov.

This has multiple advantages:

• We run ruby-versions workflow just once and pass it to the test workflows
• We can observe all tests running from a single workflow UI
• We run codecov after all coverage reports were submitted
• It looks cool 👇🏻

#skip-changelog

[solnic]

@sl0thentr0py final touch is to set up codecov token because:

==> Running send-notifications
      ./codecov send-notifications --sha 2c8238d6d9b9e52e9bcfb8b19de5932f680555d4 --git-service github
info - 2025-02-19 13:42:16,580 -- ci service found: github-actions
info - 2025-02-19 13:42:16,989 -- Process Upload Completion complete
error - 2025-02-19 13:42:16,990 -- Upload Completion failed: {"message":"Token required because branch is protected"}

[sl0thentr0py]

the secret CODECOV_TOKEN is available to all sentry repos orgwide

          token: ${{ secrets.CODECOV_TOKEN }}

[sl0thentr0py]

pretty, ty!

[st0012]

This is the most advanced GH Actions usage I've seen in Ruby projects 🤯 Very impressive improvement 👏