From "The effects of higher-order state and control on local relational reasoning"

TODO: Need to do the same for the stack proof.
TODO: Unfolding should be automatic.

rel_apply_ tactic pose the lemma before searching for a place to apply
it.
This is in accordance with <https://gitlab.mpi-sws.org/FP/iris-coq/commit/211dc7cad10da872d2840f73acd85eed0b82f7b4>