feat(data/dfinsupp/basic): add missing lemmas about `single` (#14815)
feat(data/dfinsupp/basic): add missing lemmas about `single` (#14815)

These lemmas were missed in #13076:

* `comap_domain_single`
* `comap_domain'_single`
* `sigma_curry_single`
* `sigma_uncurry_single`
* `extend_with_single_zero`
* `extend_with_zero`

These are useful since many induction principles replace a generic `dfinsupp` with `dfinsupp.single`.





leanprover-community/mathlib,leanprover-community/mathlib