RFR: 2527: Sponsored commits may get wrong author

[Zhao Song]

When determining the author of a commit, if the author of pr doesn't have OpenJDK Id, the bot falls back to use the author from the last commit of the pr, in this way, the bot may give credit to the wrong person. 
In this patch, if the author of pr doesn't have OpenJDK Id, the bot will try to parse full name and email from the forge first, if it fails, then it will fall back to use the author of the last commit.

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Commit messages:
 - SKARA-2527

Changes: https://git.openjdk.org/skara/pull/1726/files
  Webrev: https://webrevs.openjdk.org/?repo=skara&pr=1726&range=00
  Issue: https://bugs.openjdk.org/browse/SKARA-2527
  Stats: 6 lines in 1 file changed: 4 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/skara/pull/1726.diff
  Fetch: git fetch https://git.openjdk.org/skara.git pull/1726/head:pull/1726

PR: https://git.openjdk.org/skara/pull/1726