RFR: forge: add HostedRepository.recentCommitComments

[Erik Helin]

Hi all,

please review this patch that adds the method `HostedRepository.recentCommitComments` for fetching recent commit
comments. "Recent" is somewhat fuzzy and is up to the forge to decide, because the REST APIs for GitHub and GitLab are
very different for retrieving recent commit comments. The GitLab REST API in particular is a bit annoying since it
doesn't provide a `noteable_id` with the commit's hash for commit comment events. I therefore hade to make
`CommitComment` support lazily fetching the hash for the commit.

Thanks,
Erik

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Commit messages:
 - forge: add HostedRepository.recentCommitComments

Changes: https://git.openjdk.java.net/skara/pull/891/files
 Webrev: https://webrevs.openjdk.java.net/?repo=skara&pr=891&range=00
  Stats: 213 lines in 7 files changed: 176 ins; 20 del; 17 mod
  Patch: https://git.openjdk.java.net/skara/pull/891.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/891/head:pull/891

PR: https://git.openjdk.java.net/skara/pull/891