Proofs by Joshua Yanowski

This reverts commit ec5b6bd8.

The FIXME seems to not just rely on https://github.com/coq/coq/issues/5735
since it fails with Coq 8.10 and 8.11

clarify Pmap_raw comment

See merge request !229

Add several simple lemmas (mostly about list and map filter).

See merge request !226

Avoid relying on buggy simpl never behavior

See merge request iris/stdpp!228

Alternate take on
https://gitlab.inria.fr/bertot/stdpp/-/commit/895121f919c6f1332f41f658ce7f850e391eb49e,
which is used as an overlay in Coq for
https://github.com/coq/coq/pull/13448.

add Nat_iter_mul

See merge request !227

add pred_infinite_surj

See merge request iris/stdpp!225

rename elem_of_equiv_L -> set_eq, and set_equiv_spec_L -> set_eq_subseteq

See merge request iris/stdpp!210

rename elem_of_equiv -> set_equiv and set_equiv_spec -> set_equiv_subseteq, and rename some instances to get out of the way

Add `eunify` tactic that lifts Coq's `unify` tactic to `open_constr`

See merge request iris/stdpp!224

Rename `Forall_Forall2` → `Forall_Forall2_diag`

See merge request iris/stdpp!223

names for big operators in Iris.

Rename `_11` and `_12` suffixes into `_1_1` and `_1_2`

See merge request iris/stdpp!222

Fix documentation of `select` to state that it selects the "last" hypothesis.

See merge request iris/stdpp!221

Various `omap` lemmas for finite maps; generalize `map_size_{insert,delete}`.

See merge request iris/stdpp!206