With actionsFromSelf, Forgejo resolves bare `uses: actions/<name>` against
the forge itself, so every action a workflow names needs a mirror there.
Only actions/checkout was seeded, and coverage.yml's
`actions/upload-artifact@v3` has failed at job setup with "repository not
found" since the CI runner moved to swarm-ci-runner (e2da5509).
The single hardcoded checkout mirror becomes a list of action names both
share, mirrored from github.com/actions/* like checkout already was. v3
points at the same commit (ff15f03) on github.com and code.forgejo.org.
The controller's forge-objects pass creates any missing mirror on every
pass, and the changed SWARM_CONTROLLER_FORGE_MIRRORS env restarts the unit
on switch, so an existing forge picks the mirror up on deploy.
Closes#5040
9b711d5ffa