fix --time-limit

It got broken in several ways by the streaming seeking optimisations
around version 8.20201007.

Moved time limit checking out of the matcher, which was a hack in the
first place. So everywhere that uses Limit.getMatcher needs to check
time limit. Well, almost everywhere. Command.Info uses it, but it does
not make sense to time limit getting info. And Command.MultiCast uses it
just to build up a list of files that then get passed to a command, so
it would never have hit the timeout in a useful way.

This implementation is a little more expensive when at time limit than
necessary, since it continues seeking only to discard everything after the
time limit. I did try making it close the file handles to force a faster
shutdown, but that didn't work and hung. Could certianly be improved
somehow, but seeking is probably not the expensive bit when a time limit
is hit, so this seems acceptable for now.

Annex.hs

@@ -1,6 +1,6 @@
 {- git-annex monad
  -
- - Copyright 2010-2020 Joey Hess <id@joeyh.name>
+ - Copyright 2010-2021 Joey Hess <id@joeyh.name>
  -
  - Licensed under the GNU AGPL version 3 or higher.
  -}
@@ -78,6 +78,7 @@ import qualified Database.Keys.Handle as Keys
 import Utility.InodeCache
 import Utility.Url
 import Utility.ResourcePool
+import Utility.HumanTime
 
 import "mtl" Control.Monad.Reader
 import Control.Concurrent
@@ -85,6 +86,7 @@ import Control.Concurrent.STM
 import qualified Control.Monad.Fail as Fail
 import qualified Data.Map.Strict as M
 import qualified Data.Set as S
+import Data.Time.Clock.POSIX
 
 {- git-annex's monad is a ReaderT around an AnnexState stored in a MVar.
  - The MVar is not exposed outside this module.
@@ -133,6 +135,7 @@ data AnnexState = AnnexState
 	, globalnumcopies :: Maybe NumCopies
 	, forcenumcopies :: Maybe NumCopies
 	, limit :: ExpandableMatcher Annex
+	, timelimit :: Maybe (Duration, POSIXTime)
 	, uuiddescmap :: Maybe UUIDDescMap
 	, preferredcontentmap :: Maybe (FileMatcherMap Annex)
 	, requiredcontentmap :: Maybe (FileMatcherMap Annex)
@@ -201,6 +204,7 @@ newState c r = do
 		, globalnumcopies = Nothing
 		, forcenumcopies = Nothing
 		, limit = BuildingMatcher []
+		, timelimit = Nothing
 		, uuiddescmap = Nothing
 		, preferredcontentmap = Nothing
 		, requiredcontentmap = Nothing