convert .import-restrictions to yaml

yaml has comments, so we can explain why we have certain rules or
certain prefixes

for those files that weren't already commented yaml, I converted them to
yaml and took a best guess at comments based on the PRs that introduced
or updated them

pkg/controller/.import-restrictions

@@ -1,16 +1,9 @@
-{
-  "Rules": [
-    {
-      "SelectorRegexp": "k8s[.]io/kubernetes/pkg/client/unversioned$",
-      "ForbiddenPrefixes": [
-        "k8s.io/kubernetes/pkg/client/unversioned"
-      ]
-    },
-    {
-      "SelectorRegexp": "k8s[.]io/kubernetes/pkg/client/unversioned/testclient$",
-      "ForbiddenPrefixes": [
-        "k8s.io/kubernetes/pkg/client/unversioned/testclient"
-      ]
-    }
-  ]
-}
+rules:
+  # prevent use of pkg/client/unversioned (#34759)
+  - selectorRegexp: k8s[.]io/kubernetes/pkg/client/unversioned$
+    forbiddenPrefixes:
+      - k8s.io/kubernetes/pkg/client/unversioned
+  # prevent use of pkg/client/unversioned (#34759)
+  - selectorRegexp: k8s[.]io/kubernetes/pkg/client/unversioned/testclient$
+    forbiddenPrefixes:
+      - k8s.io/kubernetes/pkg/client/unversioned/testclient