Use stable Hermes for dry-run builds on stable branches (#55867)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/55867

Changelog: [Internal]

The build_android workflow was incorrectly using for dry-run
builds on stable branches (e.g., 0.85-stable), causing it to append  suffix
to the Hermes version. This resulted in trying to fetch non-existent SNAPSHOT artifacts
like in https://github.com/facebook/react-native/actions/runs/22592250332/job/65471130298.

This fix adds a check to detect stable branches (via github.ref_name or github.base_ref)
and uses  instead, which fetches the stable Hermes release from
Maven Central without the -SNAPSHOT suffix.

We check both github.ref_name and github.base_ref to cover two scenarios:
* ref_name: Direct pushes to stable branches (e.g. pushing to 0.85-stable)
* base_ref: Pull requests targeting stable branches (e.g. cherry-pick PRs where the source branch isn't named -stable but the target is)

Reviewed By: cipolleschi

Differential Revision: D95022571

fbshipit-source-id: d5888a00b29c9b5a22328fa794070c317671db2b