Milestone automation for PRs about sig-release

[spiffxp]

To make sure I understand, the GitHub queries for PR's suitable for merge would thus be:

status quo

  type:pr state:open repo:kubernetes/kubernetes 
  label:\"cncf-cla: yes\"
  label:lgtm 
  label:approved 
  -label:needs-ok-to-test
  -label:do-not-merge/hold 
  -label:do-not-merge/release-note-label-needed
  -label:do-not-merge/work-in-progress

code slush - all of the above, plus

  milestone:v1.9
  label:status/approved-for-milestone

code freeze - all of the above, plus

  label:priority/critical-urgent

Does this look right?

/cc @kubernetes/sig-testing-misc

[enisoc]

@spiffxp That looks like what I had in mind.

[enisoc]

Enabled in kubernetes/test-infra#5496.