feat(topology/connected): add `inducing.is_preconnected_image` (#11011)
feat(topology/connected): add `inducing.is_preconnected_image` (#11011)

Generalize the proof of `subtype.preconnected_space` to any `inducing`
map. Also golf the proof of `is_preconnected.subset_right_of_subset_union`.





leanprover-community/mathlib,leanprover-community/mathlib