Incorporates these changes:
- When `forgejo/build-from-sources` is present, Actions & Packages tests are run only against the built versions. Otherwise, they are run against the versions defined in `$RELEASE_NUMBERS`
- Updates Packages tests which are testing Alpine publishing to use currently supported Alpine releases
- Actions & Packages tests are run in a matrix, allowing parallel execution
Only the Actions & Packages tests take a significant amount of time (>10 minutes), so changes have been limited to those test suites -- every test suite that is moved into a matrix adds additional overhead in the 1 minute `prepare-end-to-end` step.
Reviewed-on: https://code.forgejo.org/forgejo/end-to-end/pulls/1367
Co-authored-by: Mathieu Fenniak <mathieu@fenniak.net>
Co-committed-by: Mathieu Fenniak <mathieu@fenniak.net>
