RFR: 2292: Improve the labels of Review/Commit links for backport branches

[Zhao Song]

The patch is trying to add a branch name to the commit link, review link, commit comment, review comment in JBS.

Adding a branch name for commit link and comment is feasible and easy, but adding a branch name for review link and review comment is not that easy because people can retarget pull request. Therefore, the bot needs to save the target branch name in the storage.

I believe my patch will be compatible with the existing storage files.

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Commit messages:
 - copyright
 - SKARA-2292

Changes: https://git.openjdk.org/skara/pull/1671/files
  Webrev: https://webrevs.openjdk.org/?repo=skara&pr=1671&range=00
  Issue: https://bugs.openjdk.org/browse/SKARA-2292
  Stats: 186 lines in 8 files changed: 143 ins; 10 del; 33 mod
  Patch: https://git.openjdk.org/skara/pull/1671.diff
  Fetch: git fetch https://git.openjdk.org/skara.git pull/1671/head:pull/1671

PR: https://git.openjdk.org/skara/pull/1671