chore(group_theory/subgroup): translate map comap lemmas from linear_map (#6979)
chore(group_theory/subgroup): translate map comap lemmas from linear_map (#6979)

Introduce the analogues of `linear_map.map_comap_eq` and `linear_map.comap_map_eq` to subgroups.
Also add `subgroup.map_eq_comap_of_inverse` which is a translation of `set.image_eq_preimage_of_inverse`.



Co-authored-by: Adrián Doña Mateo <39661b8dc3ffe34e47f61e03ce7eb76906251f50@users.noreply.github.com>

leanprover-community/mathlib,leanprover-community/mathlib