chore(group_theory/subgroup): rename `monoid_hom.to_range` to `monoid_hom.range_restrict` (#7218)
This makes it match:
* `monoid_hom.mrange_restrict`
* `linear_map.range_restrict`
* `ring_hom.range_restrict`
* `ring_hom.srange_restrict`
* `alg_hom.range_restrict`
This also adds a missing simp lemma.