feat(data/fin): some lemmas about casts (#8049)
feat(data/fin): some lemmas about casts (#8049)

From [LTE](https://github.com/leanprover-community/lean-liquid/blob/master/src/for_mathlib/fin.lean).



Co-authored-by: Eric <480064f38bcfd78eaf0148211ef61a38099706aa@users.noreply.github.com>

leanprover-community/mathlib,leanprover-community/mathlib