Use OWNERS-based labeling for kind/api-change

This replaces the following path-label munger config, except
we're using kind/api-change for everything instead of two
different kind/ labels

```
^pkg/api/([^/]+/)?types.go$    kind/api-change
^pkg/api/([^/]+/)?register.go$ kind/new-api
^pkg/apis/[^/]+/([^/]+/)?types.go$    kind/api-change
^pkg/apis/[^/]+/([^/]+/)?register.go$ kind/new-api
```

pkg/api/OWNERS

@@ -1,4 +1,15 @@
+# See the OWNERS docs at https://go.k8s.io/owners
+
+filters:
+  ".*":
     approvers:
       - api-approvers
     reviewers:
       - api-reviewers
+
+  # examples:
+  #   pkg/api/types.go
+  #   pkg/api/*/register.go
+  "([^/]+/)?(register|types)\\.go$":
+    labels:
+      - kind/api-change

pkg/apis/OWNERS

@@ -1,3 +1,7 @@
+# See the OWNERS docs at https://go.k8s.io/owners
+
+filters:
+  ".*":
     approvers:
     - erictune
     - lavalamp
@@ -42,3 +46,10 @@ reviewers:
     - krousey
     - rootfs
     - jszczepkowski
+
+  # examples:
+  #   pkg/apis/*/types.go
+  #   pkg/apis/*/*/types.go
+  "[^/]+/([^/]+/)?(register|types)\\.go$":
+    labels:
+      - kind/api-change