Overlay: use overlay-base CodeQL version

[cklin]

This PR changes the init action so that, in situations where it would perform overlay analysis from cache, default the CodeQL CLI version to match that from the cached overlay-base database.

Risk assessment

For internal use only. Please select the risk level of this change:

• Low risk: Changes are fully under feature flags, or have been fully tested and validated in pre-production environments and are highly observable, or are documentation or test only.

Merge / deployment checklist

• Confirm this change is backwards compatible with existing workflows.
• Consider adding a changelog entry for this change.
• Confirm the readme and docs have been updated if necessary.