split: use the new movedirstate() we now have in scmutil This avoids unnecessarily touching the working copy when splitting the parent of the working copy. That also makes the test-removeemptydirs.t case invalid, so we can just delete it. Differential Revision: https://phab.mercurial-scm.org/D6127

manifestcache: use `wcache` directory for manifest cache The manifest full text cache is tightly related to the working copy. We should use the `wcache` directory for it, instead of the `cache`. Otherwise, multiple shares would keep overwriting each other cache entry and we loose its benefit. This is also more consistent with the fact this cache file is protected by `wlock`.