YAML anchors for all verbose conditions, and precise label triggering conditions

[eddyashton]

First commit should be uncontroversial - applying the same tidy discussed in #7529 to long-verification.yml and bench-ab.yml.

Second is trying to rewrite these conditions to be more accurately triggered. Previously if you opened a PR that was already labeled, you'd get 2 separate events and 2 separate runs. and similarly if you labeled something (with any-old-junk) that also had the triggering label, we'd trigger another run. I think the correct condition is as spelt: labeled event only triggers this workflow when the relevant label is added, and the other pull_request action types only trigger this workflow if the label was present.

(NB: unlabeled is a separate event, so don't worry about triggers for removals).

This condition is now even longer and more unreadable. I think this multi-line block is valid YAML, but the GH Actions VS Code extension's language server isn't happy with it, so maybe they have a more restricted parser. Let's see what it looks like in the wild - I can flatten to one line again if necessary.

[Copilot]

Pull request overview

This PR refactors GitHub Actions workflow trigger conditions to use YAML anchors for code reusability and introduces more precise label-based triggering logic. The changes aim to prevent duplicate workflow runs when a PR is both labeled and opened/reopened simultaneously.

• Introduces YAML anchors (&check_trigger_conditions) to deduplicate verbose trigger conditions across multiple jobs
• Attempts to implement more precise label-triggering logic to distinguish between labeled events and other pull request events
• Updates three workflow files with the new trigger condition pattern

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 6 comments.

File	Description
.github/workflows/long-verification.yml	Replaces inline trigger conditions with YAML anchor and anchor references across three jobs
.github/workflows/long-test.yml	Updates the existing YAML anchor with new precise triggering logic
.github/workflows/bencher-ab.yml	Replaces inline trigger conditions with YAML anchor and anchor references across three jobs