Outputs and dependencies don't really care about the remotes, as they
don't do any pushing or pulling. What they really need are the trees,
so let's use them directly.
Part of #4050
* BaseRemote: start moving tree functions into BaseRemoteTree
* remote: add LocalRemoteTree
* remote: add cloud remote trees
* remote: move remove(), makedirs() into tree
* remote: move move(), copy(), symlink(), hardlink(), reflink() into tree
* fix attributes for moved remote methods
* tests: update unit tests for moved remote tree methods
* tests: mv unit/remote/test_remote_dir.py unit/remote/test_remote_tree.py
* fix attributes for moved remote tree functions
* tests: update func tests for moved remote tree methods
* test fixes
* fix DS warnings