Unify references to group resource in metrics
Skip apiserver_storage_objects as it's a stable metrics that doesn't
have "group" label. As defined in KEP-1209 adding a label is considered
a breaking change so this change should be done via deprecation and
introduction of new metric.
Tested via:
```
kubectl get --raw /metrics | grep -i apiservice | grep -v APIServiceRegistrationController | grep -v aggregator_unavailable_apiservice | python3 -c "import sys; print('\n'.join([k+' ' + v for k,v in {a.split('{')[0]:'{'+a.split('{')[1].split('}')[0]+'}' for a in sys.stdin.readlines() if '#' not in a and '_sum' not in a and '_bucket' not in a}.items()]))"
```
Before:
```
apiserver_cache_list_fetched_objects_total {index="",resource_prefix="/apiregistration.k8s.io/apiservices"}
apiserver_cache_list_returned_objects_total {resource_prefix="/apiregistration.k8s.io/apiservices"}
apiserver_cache_list_total {index="",resource_prefix="/apiregistration.k8s.io/apiservices"}
apiserver_longrunning_requests {component="apiserver",group="apiregistration.k8s.io",resource="apiservices",scope="cluster",subresource="",verb="WATCH",version="v1"}
apiserver_request_body_size_bytes_count {resource="apiservices.apiregistration.k8s.io",verb="create"}
apiserver_request_duration_seconds_count {component="apiserver",dry_run="",group="apiregistration.k8s.io",resource="apiservices",scope="resource",subresource="",verb="POST",version="v1"}
apiserver_request_sli_duration_seconds_count {component="apiserver",group="apiregistration.k8s.io",resource="apiservices",scope="resource",subresource="",verb="POST",version="v1"}
apiserver_request_total {code="201",component="apiserver",dry_run="",group="apiregistration.k8s.io",resource="apiservices",scope="resource",subresource="",verb="POST",version="v1"}
apiserver_response_sizes_count {component="apiserver",group="apiregistration.k8s.io",resource="apiservices",scope="cluster",subresource="",verb="LIST",version="v1"}
apiserver_selfrequest_total {resource="apiservices",subresource="",verb="POST"}
apiserver_storage_events_received_total {resource="apiservices.apiregistration.k8s.io"}
apiserver_storage_list_evaluated_objects_total {resource="apiservices.apiregistration.k8s.io"}
apiserver_storage_list_fetched_objects_total {resource="apiservices.apiregistration.k8s.io"}
apiserver_storage_list_returned_objects_total {resource="apiservices.apiregistration.k8s.io"}
apiserver_storage_list_total {resource="apiservices.apiregistration.k8s.io"}
apiserver_storage_objects {resource="apiservices.apiregistration.k8s.io"}
apiserver_watch_cache_events_dispatched_total {resource="apiservices.apiregistration.k8s.io"}
apiserver_watch_cache_events_received_total {resource="apiservices.apiregistration.k8s.io"}
apiserver_watch_cache_initializations_total {resource="apiservices.apiregistration.k8s.io"}
apiserver_watch_cache_resource_version {resource="apiservices.apiregistration.k8s.io"}
apiserver_watch_events_sizes_count {group="apiregistration.k8s.io",kind="APIService",version="v1"}
apiserver_watch_events_total {group="apiregistration.k8s.io",kind="APIService",version="v1"}
etcd_request_duration_seconds_count {operation="listWithCount",type="/registry/apiregistration.k8s.io/apiservices/"}
etcd_requests_total {operation="listWithCount",type="/registry/apiregistration.k8s.io/apiservices/"}
watch_cache_capacity {resource="apiservices.apiregistration.k8s.io"}
```
After:
```
apiserver_cache_list_fetched_objects_total {group="apiregistration.k8s.io",index="",resource="apiservices"}
apiserver_cache_list_returned_objects_total {group="apiregistration.k8s.io",resource="apiservices"}
apiserver_cache_list_total {group="apiregistration.k8s.io",index="",resource="apiservices"}
apiserver_longrunning_requests {component="apiserver",group="apiregistration.k8s.io",resource="apiservices",scope="cluster",subresource="",verb="WATCH",version="v1"}
apiserver_request_body_size_bytes_count {group="apiregistration.k8s.io",resource="apiservices",verb="create"}
apiserver_request_duration_seconds_count {component="apiserver",dry_run="",group="apiregistration.k8s.io",resource="apiservices",scope="resource",subresource="",verb="POST",version="v1"}
apiserver_request_sli_duration_seconds_count {component="apiserver",group="apiregistration.k8s.io",resource="apiservices",scope="resource",subresource="",verb="POST",version="v1"}
apiserver_request_total {code="201",component="apiserver",dry_run="",group="apiregistration.k8s.io",resource="apiservices",scope="resource",subresource="",verb="POST",version="v1"}
apiserver_response_sizes_count {component="apiserver",group="apiregistration.k8s.io",resource="apiservices",scope="cluster",subresource="",verb="WATCH",version="v1"}
apiserver_selfrequest_total {group="apiregistration.k8s.io",resource="apiservices",subresource="",verb="WATCH"}
apiserver_storage_events_received_total {group="apiregistration.k8s.io",resource="apiservices"}
apiserver_storage_list_evaluated_objects_total {group="apiregistration.k8s.io",resource="apiservices"}
apiserver_storage_list_fetched_objects_total {group="apiregistration.k8s.io",resource="apiservices"}
apiserver_storage_list_returned_objects_total {group="apiregistration.k8s.io",resource="apiservices"}
apiserver_storage_list_total {group="apiregistration.k8s.io",resource="apiservices"}
apiserver_storage_objects {resource="apiservices.apiregistration.k8s.io"}
apiserver_watch_cache_events_dispatched_total {group="apiregistration.k8s.io",resource="apiservices"}
apiserver_watch_cache_events_received_total {group="apiregistration.k8s.io",resource="apiservices"}
apiserver_watch_cache_initializations_total {group="apiregistration.k8s.io",resource="apiservices"}
apiserver_watch_cache_resource_version {group="apiregistration.k8s.io",resource="apiservices"}
apiserver_watch_events_sizes_count {group="apiregistration.k8s.io",resource="apiservices",version="v1"}
apiserver_watch_events_total {group="apiregistration.k8s.io",resource="apiservices",version="v1"}
etcd_bookmark_counts {group="apiregistration.k8s.io",resource="apiservices"}
etcd_request_duration_seconds_count {group="apiregistration.k8s.io",operation="listWithCount",resource="apiservices"}
etcd_requests_total {group="apiregistration.k8s.io",operation="listWithCount",resource="apiservices"}
watch_cache_capacity {group="apiregistration.k8s.io",resource="apiservices"}
```
Kubernetes-commit: f712b01ddb55f6569b930ca714499051ba8cb311
a559cb8be1