Fix JENKINS-75500: Report build status to GitHub merge queue

[sinedd777]

When GitHub merge queue is enabled, it creates temporary branches with different commit SHAs than the PR head. This change detects when the actual built commit differs from the PR head and reports status to the correct SHA, allowing merge queue to complete successfully.

• Check BuildData for actual built commit
• Compare with PR head commit
• Use actual commit SHA for status reporting in merge queue context

JENKINS-75500 for further information.

Submitter checklist

• Link to JIRA ticket in description, if appropriate.
• Change is code complete and matches issue description
• Automated tests have been added to exercise the changes
• Reviewer's manual test instructions provided in PR description. See Reviewer's first task below.

Reviewer checklist

• Run the changes and verify that the change matches the issue description
• Reviewed the code
• Verified that the appropriate tests have been written or valid explanation given

Documentation changes

• Link to jenkins.io PR, or an explanation for why no doc changes are needed

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