context: remove uses of manifest.matches This removes the uses of manifest.matches in context.py in favor of the new manifest.diff(match) api. This is part of removing manifest.matches since it is O(manifest). To drop the dependency on ctx._manifestmatches(s) we transfer responsibilty for creating status oriented manifests over to ctx._buildstatusmanifest(s). This already existed for workingctx, we just need to implement a simple version for basectx. The old _manifestmatches functionality is basically identical to the _buildstatusmanifest functionality (minus the matching part), so no behavior should be lost.