ci: only satisfy pre-checks once merge requested

[mhofman]

Description

#8253 left in place the cancellation of any concurrent pull request integration test, because of #6466

Unfortunately that resulted in mergify offboarding a PR that had been labelled force:integration right when adding an automerge: label because:

• all required checks had already succeeded (except for merge strategy chosen)
• adding the automerge: label immediately satisfied the merge strategy chosen checks, and thus onboarded the PR onto the queue
  • the wait-integration-pre-checks check was already marked as success because of the force:integration label
  • the merge was pending on getting a integration-test-result check status
• Actions triggered a new run of Integration tests
  • The concurrent rules caused the cancellation of the existing run (known limitation due to CI is re-running successful skipped jobs #6466)
  • integration-test-result reported a failure because of the run cancellation (we need that behavior to solve Mergify stall on getting-started local-npm failure #6014 and Failed GH Action reports as skipped, bypassing merge checks #7126)
  • Problem: mergify offboarded the PR because "The queue conditions cannot be satisfied due to failing checks."

This PR tweaks the wait-integration-pre-checks check to only report a success once the PR is labelled with an automerge: label, instead of also allowing force:integration. This is not foolproof as cancellations may still happen if changing labels after adding the automerge: label, however that should be much less common an occurrence.

The right solution would be remove the GH managed concurrent check and restore the one based on source tree, aka solve #6466

Security Considerations

None

Scaling Considerations

None

Documentation Considerations

Add this known limitation to the wiki

Testing Considerations

Manually on this PR

Upgrade Considerations

None