Fix #32795
If a job uses a matrix, multiple `ActionRunJobs` may have the same
`JobID`. We need to merge the outputs of these jobs to make them
available to the jobs that need them.
(cherry picked from commit 7269130d2878d51dcdf11f7081a591f85bd493e8)
Conflicts:
models/fixtures/action_run.yml
models/fixtures/action_run_job.yml
trivial context conflicts
Fixes #28853
Needs both https://gitea.com/gitea/act_runner/pulls/473 and
https://gitea.com/gitea/act_runner/pulls/471 on the runner side and
patched `actions/upload-artifact@v4` / `actions/download-artifact@v4`,
like `christopherhx/gitea-upload-artifact@v4` and
`christopherhx/gitea-download-artifact@v4`, to not return errors due to
GHES not beeing supported yet.
(cherry picked from commit a53d268aca87a281aadc2246541f8749eddcebed)