[WIP] Add certificate reconciler for internal certs

[nak3]

This patch changes to add certificate reconciler for internal certs

This is an alternative idea of #12998.
Feature track mentioned about both this and using cert-manager.

[knative-prow]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: nak3

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Details

Needs approval from an approver in each of these files:

• OWNERS [nak3]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[codecov]

Codecov Report

Merging #13000 (0466d26) into main (bb5bdbb) will not change coverage.
The diff coverage is 0.00%.

@@           Coverage Diff           @@
##             main   #13000   +/-   ##
=======================================
  Coverage   87.01%   87.01%           
=======================================
  Files         197      197           
  Lines       14439    14439           
=======================================
  Hits        12564    12564           
  Misses       1580     1580           
  Partials      295      295           

Impacted Files	Coverage Δ
cmd/activator/main.go	0.00% <0.00%> (ø)
cmd/controller/main.go	0.00% <ø> (ø)
cmd/queue/main.go	0.64% <ø> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update bb5bdbb...0466d26. Read the comment docs.

[knative-prow-robot]

@nak3: PR needs rebase.

Details

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.