add startup sequence duration and readyz endpoint
add rbac bootstrapping policy for readyz
add integration test around grace period and readyz
rename startup sequence duration flag
copy health checks to fields
rename health-check installed boolean, refactor clock injection logic
cleanup clock injection code
remove todo about poststarthook url registration from healthz
Kubernetes-commit: 54dcf5c9c46fc4782d4861936309349b5a71a1ac
wojtekt
Han Kang