v2: Implementation

[ymmt2005]

What

Implement Coil v2 features:

• Use CRD to configure Coil instead of CLI tool coilctl.
• Use CRD/ConfigMap to store status data.
• Decouple the pool name and namespace name. Use annotations to specify the pool to be used.
• Use gRPC instead of REST for local inter-process communication.
• Use CRD for communication between the controller and the node pods.
• Use leader-election of the controller for better availability.
• Implement egress NAT using foo-over-udp.
• Prometheus metrics including Go runtime and gRPC.

How

Completely rewrite the code under v2/ directory.
All codes from v1 are moved under v1/ directory.

Checklist

• Finish implentation of the issue
• Test all functions
• Have enough logs to trace activities
• Notify developers of necessary actions