`hg strip` and other things that use repair.strip (such as the narrow
extension's `hg tracked --removeinclude`) will "save" some commits that have a
higher revision number than the oldest commit we're stripping, but aren't
actually descended from any of the commits that we're stripping. It saves them
in a bundle, and then reapplies them to the repo.

Remotefilelog doesn't generally participate in strip, it doesn't contribute
files to either the backup bundle or the "saved" bundle, and doesn't adjust
linknodes when commits are stripped. This can break things like push, which
rely on the linknodes.

This change makes it so that remotefilelog includes files in these bundles
during strip operations. During reapplication, the files are reapplied from the
bundle, and the linknode is properly updated.

Differential Revision: https://phab.mercurial-scm.org/D10320