copies-rust: rename TimeStampedPathCopies to InternalPathCopies We are looking into moving away from TimeStampedPathCopy (that use is_ancestors call to detect overwrite) in favor of an approach that does not requires is_ancestors calls. Yet we will still need an internal representation that differs from the returned result. So we call it "InternalPathCopies" which is generic but clear. Differential Revision: https://phab.mercurial-scm.org/D9641