feat(data/fintype/basic): `one_lt_card_iff` and `two_lt_card_iff` (#11524)
feat(data/fintype/basic): `one_lt_card_iff` and `two_lt_card_iff` (#11524)

This PR adds `one_lt_card_iff` and `two_lt_card_iff`.





leanprover-community/mathlib,leanprover-community/mathlib