RFR: 1860: Make it possible to configure PR bot to jcheck all commits in "Merge PR" [v3]

[Zhao Song]

> In this patch, PR bot has been added with the capability to control whether jcheck every commit in a merge PR.
> 
> By default, jcheckMerge is enabled.
> 
> However, if it is desired to enable jcheckMerge in a repo, the configuration can be added to the PR bot configuration as follows:
> 
> {
>   "pr": {
>       "repositories": {
>           "repo1": {
>                "jcheckMerge": true
>           }
>        }
>   }
> }
> 
> If jcheckMerge is true, then the pr bot would jcheck all the commits in the merge PR and if any jcheck doesn't pass, the error message will be treated as Integration blocker.

Zhao Song has updated the pull request incrementally with one additional commit since the last revision:

  remove try catch when running jchecks

-------------

Changes:
  - all: https://git.openjdk.org/skara/pull/1510/files
  - new: https://git.openjdk.org/skara/pull/1510/files/0a436875..39288068

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=skara&pr=1510&range=02
 - incr: https://webrevs.openjdk.org/?repo=skara&pr=1510&range=01-02

  Stats: 115 lines in 3 files changed: 69 ins; 13 del; 33 mod
  Patch: https://git.openjdk.org/skara/pull/1510.diff
  Fetch: git fetch https://git.openjdk.org/skara.git pull/1510/head:pull/1510

PR: https://git.openjdk.org/skara/pull/1510