Factor out upsert and upsertAndWait

It's a common pattern in the create commands to construct a value,
then (if not exporting it) upsert it and wait for it to
reconcile. This commit factors `upsert`, which does the update/insert
bit, and `upsertAndWait`, which does the whole thing.

Since these output messages, they are methods of `apiType` (previously
`names`), so that they have access to the name of the kind they are
operating on.

Signed-off-by: Michael Bridgen <michael@weave.works>

cmd/flux/get_image_policy.go

@@ -33,8 +33,8 @@ var getImagePolicyCmd = &cobra.Command{
   flux get image policy --all-namespaces
 `,
 	RunE: getCommand{
-		names: imagePolicyNames,
-		list:  &imagePolicyListAdapter{&imagev1.ImagePolicyList{}},
+		apiType: imagePolicyType,
+		list:    &imagePolicyListAdapter{&imagev1.ImagePolicyList{}},
 	}.run,
 }