Patch fixes MockIndexOutputWrapper to always call delegate.close().
On the way, I fixed TestPersistentSnapshotDeletionPolicy to always close the PSDP, as well as fixed a "leak" in PSDP itself.
I will commit this one. There are still tests that fail to delete directories, but I think we should iterate on them separately, as all seem to be related to how MockIOWrapper handles those maybeThrowDeterminsticEx. I'll send a separate mail.
This issue is about fixing LTC so that it outputs more information about directories that fail to delete. You can simulate failures, on Windows, by running tests w/ -Dtests.directory=FSDirectory, then track the stacktraces that are printed.