WIP: In activity title, include a link to the git branch or tag name

What does this MR do?

In this MR, we append the branch_link to Chat message push notification activity titles. This allows services like MS Teams to display push messages with meaningful links to the Git branch or tag name.

Note to reviewers:

• Several private helper methods were added to push_message.rb that allow us to: ** Invoke a new action_title helper from activity to return an appropriate formatted string ** Allow users to see the same activity messages whether we are surfacing the results with or without markdown enabled
• push_message_spec.rb unit tests updated to reflect updated activity message format

What are the relevant issue numbers?

Closes #51959 (closed)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• Tests added for this feature/bug
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides
• Link to e2e tests MR added if this MR has Requires e2e tests label. See the Test Planning Process.