use getSymbolicLinkStatus not getFileStatus to avoid crash on broken symlink

Fix crash importing from a directory special remote that contains a broken
symlink.

The crash was in listImportableContentsM but some other places in
Remote.Directory also seemed like they could have the same problem.

Also audited for other places that have such a problem. Not all calls
to getFileStatus are bad, in some cases it's better to crash on something
unexpected. For example, `git-annex import path` when the path is a broken
symlink should crash, the same as when it does not exist. Many of the
getFileStatus calls are like that, particularly when they involve
.git/annex/objects which should never have a broken symlink in it.

Fixed a few other possible cases of the problem.

Sponsored-by: Lawrence Brogan on Patreon

Git.hs

@@ -156,7 +156,7 @@ hookPath script repo = do
 #if mingw32_HOST_OS
 	isexecutable f = doesFileExist f
 #else
-	isexecutable f = isExecutable . fileMode <$> getFileStatus f
+	isexecutable f = isExecutable . fileMode <$> getSymbolicLinkStatus f
 #endif
 
 {- Makes the path to a local Repo be relative to the cwd. -}