feat: Centralize leaked ENI cleanup

[sushrk]

Issue #, if available:
N/A
Description of changes:
Centralize leaked ENI cleanup in the controller to delete leaked ENIs provisioned by the controller and VPC-CNI:

• Added finalizer in CNINode: when kubernetes deletes an object that has finalizers specified for it, the Kubernetes API marks the object for deletion by populating .metadata.deletionTimestamp, and returns a 202 status code (HTTP "Accepted"). The target object remains in a terminating state while the control plane, or other components, take the actions defined by the finalizers. After these actions are complete, the controller removes the relevant finalizers from the target object. When the metadata.finalizers field is empty, Kubernetes considers the deletion complete and deletes the object.
• Add a new field in Spec to add Tag: This is currently used to specify tags that need to added to network interfaces provisioned by the controller and VPC-CNI. VPC-CNI will read the CNINode to get the tags.

The CNINode reconciler will add the finalizer and tag if missing on existing CNINode objects and handles the finalizer routine to clean up leaked resources.

• Re-create CNINode if deleted by user: The controller will re-create CNINode if deleted by user when node object is still present.
  If failed to create, node event will be published:

  Warning  CNINodeDeleted                  2m7s  vpc-resource-controller  CNINode was deleted and could not be re-created by controller

• Removed deleting branch ENIs on node termination
• Added metrics to count number of available ENIs found and number of leaked ENIs that failed to be deleted
• Added metrics to count the number of times controller needed to recreate CNINode
  Tests:

SGPP test suite

Ran 19 of 23 Specs in 923.345 seconds
SUCCESS! -- 19 Passed | 0 Failed | 0 Pending | 4 Skipped
PASS

Ginkgo ran 1 suite in 15m25.59382642s
Test Suite Passed

• Verified CNINode finalizers and tags are added(if missing) to existing CNINode objects
• Verified finalizer routine is called when CNINode object is deleted at node termination
• Verified CNINode is re-created when deleted if the node object exists
• Verified new metrics are registered on the controller

Note, PR for the test suite is pending until the changes are merged in.

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[sushrk]

Had a sync offline, and addressed all the comments in subsequent commits. PTAL, thanks.

[haouc]

lgtm