RFR: 2198: Backport PRs should check if a CSR is required [v5]

[Zhao Song]

> This patch is trying to let the pr bot automatically requires csr for a backport PR if one of the associated has a resolved CSR.

Zhao Song has updated the pull request incrementally with two additional commits since the last revision:

 - update
 - update

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

Changes:
  - all: https://git.openjdk.org/skara/pull/1623/files
  - new: https://git.openjdk.org/skara/pull/1623/files/a20024f8..1a8aa85a

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=skara&pr=1623&range=04
 - incr: https://webrevs.openjdk.org/?repo=skara&pr=1623&range=03-04

  Stats: 34 lines in 1 file changed: 18 ins; 5 del; 11 mod
  Patch: https://git.openjdk.org/skara/pull/1623.diff
  Fetch: git fetch https://git.openjdk.org/skara.git pull/1623/head:pull/1623

PR: https://git.openjdk.org/skara/pull/1623