remotefilelog: rename wireproto methods and remaining capabilities This is a mess, in part because there should be more constants throughout. I know we typically do exp- instead of the x_ business in this change, but I also had to use this in some function names, so I figured until I can break that coupling I'd go with this. If it's too unpleasant during review, let me know and I can probably clean it up some more. # no-check-commit due to new foo_bar naming - too hard to avoid right now :( Differential Revision: https://phab.mercurial-scm.org/D5129

remotefilelog: consolidate and rename on-disk store requirement The value of this constant appeared in too many places. While we're here, rename it to be more consistent with our naming conventions for experimental functionality. Differential Revision: https://phab.mercurial-scm.org/D5128