feat(algebra/big_operators/basic): add `prod_dite_of_false`, `prod_dite_of_true` (#8865)
feat(algebra/big_operators/basic): add `prod_dite_of_false`, `prod_dite_of_true` (#8865)

The proofs are not mine cf [Zulip conversation](https://leanprover.zulipchat.com/#narrow/stream/217875-Is-there.20code.20for.20X.3F/topic/.60prod_dite_of_true.60)

Co-authored-by: Adam Topaz <64b2b6d12bfe4baae7dad3d018f8cbf6b0e7a044@adamtopaz.com>
Co-authored-by: Eric Rodriguez <58774b6ca42a471874700e44c6b2ee898872147e@gmail.com>





leanprover-community/mathlib,leanprover-community/mathlib