feat(controlplane): Add cache init sync duration for control planes

[randmonkey]

What this PR does / why we need it:
Add cache.initSyncDuration to configure the init cache sync delay as --iniit-cache-sync-duration does in KIC.
Which issue this PR fixes

Part of Kong/kong-operator#1796

Special notes for your reviewer:
Naming:

• Should we name the parent field to some names like k8sCache to indicate that this is for the configuration related to the k8s object cache?
• Should we name the field to initSyncDelay as it should be more accurate than initSyncDuration?
  PR Readiness Checklist:

Complete these before marking the PR as ready to review:

• the CHANGELOG.md release notes have been updated to reflect significant changes