Checkpoint some progress on [find_subtree_rename_oob], which should help with proving [rename_safe_dest_none].
Checkpoint some progress on [find_subtree_rename_oob], which
should help with proving [rename_safe_dest_none].

mit-pdos/fscq-impl,mit-pdos/fscq-impl,mit-pdos/fscq-impl,mit-pdos/fscq-impl,mit-pdos/fscq-impl