Add option for disabling leader election

[ChenYi015]

Purpose of this PR

Close #2384

Proposed changes:

• Add option controller.leaderElection.enable and webhook.leaderElection.enable for disabling controller/webhook leader election
• When leader election was disabled, the related RBAC rules against leases will be removed.

Change Category

• Bugfix (non-breaking change which fixes an issue)
• Feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that could affect existing functionality)
• Documentation update

Rationale

Checklist

• I have conducted a self-review of my own code.
• I have updated documentation accordingly.
• I have added tests that prove my changes are effective or that my feature works.
• Existing unit tests pass locally with my changes.

Additional Notes

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[ChenYi015]

/assign @jacobsalway

[jacobsalway]

Does it make sense to have leader election on the webhook at all? It's a mostly stateless service that can have multiple replicas. The only part that might be relevant to have leader election on is the TLS certificate generation/setting the secret, but this only needs to be done once and exponentially retries on conflict or error anyway so I think it's fine if multiple replicas attempt to do this.

The core of this PR looks good to me though. Happy to tick and add a separate PR for removing leader election.