RFR: 1858: Make it possible to configure to require reviewers for "Merge" PRs [v4]

[Zhao Song]

> In this patch, PR bot has been added with the capability to control the requirement of reviews for merge pull requests.
> 
> By default, review is not necessary for merge pull requests.
> 
> However, if it is desired to enable the requirement of reviews for merge requests in a repo, the configuration can be added to the PR bot configuration as follows:
> 
> {
>   "pr": {
>       "repositories": {
>           "repo1": {
>                "reviewMergePullRequest": true
>           }
>        }
>   }
> }
> 
> 
> Currently, jcheck would run in two places in skara bot. One is in checkRun and one is in IntegrateCommand. For the merge pull requests that not require review, the Reviewers check would be skipped.
> 
> The other way to run jcheck in using SKARA CLI. This patch is also compatible with it.

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

  fix some problems

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

Changes:
  - all: https://git.openjdk.org/skara/pull/1495/files
  - new: https://git.openjdk.org/skara/pull/1495/files/838677d9..75a8b7b2

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=skara&pr=1495&range=03
 - incr: https://webrevs.openjdk.org/?repo=skara&pr=1495&range=02-03

  Stats: 4 lines in 2 files changed: 3 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/skara/pull/1495.diff
  Fetch: git fetch https://git.openjdk.org/skara.git pull/1495/head:pull/1495

PR: https://git.openjdk.org/skara/pull/1495