[github-actions] Fix packaged PHP version resolver action path

[coisa]

Summary

The reusable workflows introduced for PHP version inference reference a composite action in a path that is excluded from GitHub's archive payload, causing workflow runs to fail with:

Can't find 'action.yml', 'action.yaml' or 'Dockerfile' for action 'php-fast-forward/dev-tools/.github/actions/resolve-php-version@main'.

Problem

The resolver action was placed under .github/actions/..., but this repository marks /.github/ as export-ignore in .gitattributes.
When GitHub resolves uses: owner/repo/path@ref, it fetches the repository archive for that ref. Because .github/ is excluded, the action metadata file is missing at runtime.

A follow-up attempt to place the action under resources/github-actions/... would also be problematic because dev-tools:sync copies that directory into consumer workflow paths.

Acceptance Criteria

• Move the composite action to a packaged path that is included in GitHub action archives.
• Keep the action outside .github/ so export-ignore does not strip it.
• Keep the action outside resources/github-actions/ so dev-tools:sync does not copy it into consumer .github/workflows.
• Update wiki.yml, reports.yml, and tests.yml to reference the new action path.
• Validate the affected workflow YAML files after the path change.

Non-goals

• Reworking the PHP version resolution logic itself.
• Reintroducing workflow-ref checkouts for the resolver bootstrap.