Enable HA for runtime-enforcer operator

[holyspectral]

Currently we have only one replica of operator by default. This can easily cause service disruption, e.g., when a node is down.

Luckily controller-runtime supports leader election. We just need to adjust the replicas of operator, enable the leader election if it's disabled, and make sure that our code isn't broken.

Acceptance criteria:

• Increase the default replicas to 2.
• Make sure that when the leader pod is down, other pod can take over.
• E2E test to cover this scenario if possible.