RFR: 1663: Mark integrated Pull Requests as properly merged in GitHub repositories [v6]

[Julian Waters]

> WIP

Julian Waters has updated the pull request incrementally with one additional commit since the last revision:

  Implement by giving the Pull Request bots their own integration branch feature instead

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Changes:
  - all: https://git.openjdk.org/skara/pull/1409/files
  - new: https://git.openjdk.org/skara/pull/1409/files/804df720..1e79c875

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=skara&pr=1409&range=05
 - incr: https://webrevs.openjdk.org/?repo=skara&pr=1409&range=04-05

  Stats: 29 lines in 2 files changed: 19 ins; 1 del; 9 mod
  Patch: https://git.openjdk.org/skara/pull/1409.diff
  Fetch: git fetch https://git.openjdk.org/skara pull/1409/head:pull/1409

PR: https://git.openjdk.org/skara/pull/1409