[release-1.6] Add k8s field to base component

[istio-testing]

Manual cherrypick required.

#1465 failed to apply on top of branch "release-1.6":

error: Failed to merge in the changes.
Using index info to reconstruct a base tree...
M	operator/v1alpha1/istio.operator.v1alpha1.pb.html
M	operator/v1alpha1/operator.pb.go
M	operator/v1alpha1/operator.proto
M	python/istio_api/operator/v1alpha1/operator_pb2.py
Falling back to patching base and 3-way merge...
Auto-merging python/istio_api/operator/v1alpha1/operator_pb2.py
CONFLICT (content): Merge conflict in python/istio_api/operator/v1alpha1/operator_pb2.py
Auto-merging operator/v1alpha1/operator.proto
CONFLICT (content): Merge conflict in operator/v1alpha1/operator.proto
Auto-merging operator/v1alpha1/operator.pb.go
CONFLICT (content): Merge conflict in operator/v1alpha1/operator.pb.go
Auto-merging operator/v1alpha1/istio.operator.v1alpha1.pb.html
Patch failed at 0001 Add k8s field to base component