[ci]: add workflow to bump canary after backport (#92801)
This adds an automated path to keep canary semver-ahead after a
successful stable backport publish.
Today, a backport release can produce a stable version that is newer
than the current canary version, which creates confusing version
ordering for tooling. This change adds a follow-up workflow that
evaluates completed backport publishes and, when appropriate, triggers a
canary preminor release on canary.
The `Sync Canary After Backport Release` workflow evaluates whether a
completed `build-and-deploy` run should trigger a canary sync.
The evaluation only triggers when:
- the upstream `Potentially publish release` job succeeded
- the head commit is a stable release commit
- the published stable version is a backport relative to next@latest
- the current canary version is not already semver-ahead
- there is not already a queued or in-progress Trigger Release run on
canary
When all checks pass, the workflow dispatches trigger_release.yml on
canary with:
- releaseType=canary
- semverType=minor
- force=true
(This is currently gated behind an env flag so we can dry-run it)
