RFR: 1851: Fold CSR bot into PR bot [v5]

[Zhao Song]

> In this patch, the whole csr bot module is removed. 
> 
> Original CSRPullRequestBot is deleted. The functionality of this bot has been moved to `CheckRun`.
> 
> Original CSRIssueBot has been moved to pr bot module. PullRequestBotFactory would generate a CSRIssueBot for every configured Issue project.

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

  improve some comments

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

Changes:
  - all: https://git.openjdk.org/skara/pull/1492/files
  - new: https://git.openjdk.org/skara/pull/1492/files/c5990274..edfd7b09

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=skara&pr=1492&range=04
 - incr: https://webrevs.openjdk.org/?repo=skara&pr=1492&range=03-04

  Stats: 5 lines in 3 files changed: 0 ins; 0 del; 5 mod
  Patch: https://git.openjdk.org/skara/pull/1492.diff
  Fetch: git fetch https://git.openjdk.org/skara.git pull/1492/head:pull/1492

PR: https://git.openjdk.org/skara/pull/1492