store: issue a single entry for each revlog We now yield a single entry, with data about each files involved. This help to simplify multiple code using this and it will help to further simplify and fixes the streaming code.

store: rename `unencoded_path` to `entry_path` for StoreEntry This remove the ambiguity with StoreFile and make sure use code will be using the right API.

store: do the revlog matching on entry directly This is the last blocker to safely merge the revlog files in a single entry.

store: split the wrapping of encodedstore between _wrap and datafiles The `datafiles` method of `basicstore` is doing a lot of work that should be done on decoded filename. So we now wrap `_walk` to do the decoding, and less work in `datafiles`. This is necessary to make sure file from the same revlog can be grouped together.

store: introduce a main_file_path method for revlog This help code that need to point revlog to an index file. This is put to use in the upgrade code.

upgrade: actually use StoreEntry API to create revlog Lets make use of the semanctic of the object we are passed.

upgrade: use StoreEntry object in upgrade We will make more use of the API in the next changeset, but just moving to use entry is a significant change for the engine codebase.

upgrade: drop a quick fix that is not longer necessary We won't issue bad revlog from topfile anymore.

store: use StoreEntry API instead of parsing filename in largefile This is more explicit and more robust.

store: use StoreEntry API instead of parsing filename when listing manifestlog This is more explicit and more robust.