arrange for regional output manager to run when -J is enabled

Commands that want to use it have to run their seek action inside
allowConcurrentOutput. Which seems reasonable; perhaps some future command
will want to support the -J flag but not use regions.

The region state moved from Annex to MessageState. This makes sense
organizationally, and note that some uses of onLocal use a different Annex
state, but pass the MessageState into it, which is what is needed.

Command/Get.hs

@@ -37,7 +37,7 @@ optParser desc = GetOptions
 	<*> optional (parseKeyOptions True)
 
 seek :: GetOptions -> CommandSeek
-seek o = do
+seek o = allowConcurrentOutput $ do
 	from <- maybe (pure Nothing) (Just <$$> getParsed) (getFrom o)
 	withKeyOptions (keyOptions o) (autoMode o)
 		(startKeys from)