[skara] RFR: forge: pass commit-title-to-commits map to GitLab

[Erik Helin]

Hi all,

please review this patch that greatly simplifies `GitLabRepository.recentCommitComments`. Now that `CommitCommentsWorkItem` has a `Repository` instance anyhow for filtering out applicable commits, we can use that to create a "commit titles to commits" map and pass that to `GitLabRepository.recentCommitComments`. This greatly speeds up the function call (avoid a bunch of expensive REST requests). Other forges can just ignore the argument.

Thanks,
Erik

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Commit messages:
 - forge: pass commit-title-to-commits map to GitLab

Changes: https://git.openjdk.java.net/skara/pull/1035/files
 Webrev: https://webrevs.openjdk.java.net/?repo=skara&pr=1035&range=00
  Stats: 100 lines in 6 files changed: 30 ins; 57 del; 13 mod
  Patch: https://git.openjdk.java.net/skara/pull/1035.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/1035/head:pull/1035

PR: https://git.openjdk.java.net/skara/pull/1035