Bug 2037926 - grant file-specific version_bump scopes to staging-xpi-manifest

[JohanLorenzo]

Summary

• Adds project:releng:lando:action:version_bump:file:browser/extensions/newtab/manifest.json and project:releng:lando:action:version_bump:file:browser/extensions/webcompat/manifest.json scopes to staging-xpi-manifest
• Keeps the existing general project:releng:lando:action:version_bump during the transition period (removed in the cleanup PR)
• Staging-only change; production grants are handled in the cleanup PR

Merge order

1. This PR (fxci-config staging) — apply-staging + merge
2. scriptworker-scripts #1448 — deploy to staging via dev-landoscript, merge to master
3. fxci-config production #1038 — after staging verification
4. mozilla-taskgraph #215 — merge + publish
5. xpi-manifest — update mozilla-taskgraph pin, trigger staging e2e test
6. firefox gecko_taskgraph — Phabricator + uplift
7. fxci-config cleanup (separate PR) — remove old general version_bump grants
8. scriptworker-scripts cleanup (separate PR) — remove transition fallback

Verification

Apply staging with /taskcluster apply-staging, then trigger a staging-xpi-manifest release-promotion (ship phase). Verify the version-bump-* task succeeds with the file-specific scopes.

Bug 2037926

[jcristau]

Could also make this browser/extensions/*, but we can leave it like this for now and reconsider if/when we need to add more.

[JohanLorenzo]

Sounds good. Let's reconsider it when we need to add more.