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/delete_image_policy.go

@@ -30,8 +30,8 @@ var deleteImagePolicyCmd = &cobra.Command{
   flux delete auto image-policy alpine3.x
 `,
 	RunE: deleteCommand{
-		names:  imagePolicyNames,
-		object: universalAdapter{&imagev1.ImagePolicy{}},
+		apiType: imagePolicyType,
+		object:  universalAdapter{&imagev1.ImagePolicy{}},
 	}.run,
 }