RFR: 2347: SKARA Bot can't find the commit in GitHub if the commit isn't in the default branch

[Zhao Song]

When searching for a commit in GitHub, the Skara bot utilizes the /search/commits API to look for commits in the whole organization. However, this API has a limitation: it can only find commits in the default branch of each repository. Therefore, If the commit is not found using /search/commits, the bot should try to locate it in each repository.

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Commit messages:
 - SKARA-2347

Changes: https://git.openjdk.org/skara/pull/1684/files
  Webrev: https://webrevs.openjdk.org/?repo=skara&pr=1684&range=00
  Issue: https://bugs.openjdk.org/browse/SKARA-2347
  Stats: 33 lines in 1 file changed: 24 ins; 5 del; 4 mod
  Patch: https://git.openjdk.org/skara/pull/1684.diff
  Fetch: git fetch https://git.openjdk.org/skara.git pull/1684/head:pull/1684

PR: https://git.openjdk.org/skara/pull/1684