Big-operators lemmas about star algebraic operations

These results are kept separate from Algebra.Star.Basic to avoid it needing to import Finset.

@[simp]

theorem star_prod {R : Type u_1} [CommMonoid R] [StarMul R] {α : Type u_2} (s : Finset α) (f : α → R) : star (∏ x ∈ s, f x) = ∏ x ∈ s, star (f x)

@[simp]

theorem star_sum {R : Type u_1} [AddCommMonoid R] [StarAddMonoid R] {α : Type u_2} (s : Finset α) (f : α → R) : star (∑ x ∈ s, f x) = ∑ x ∈ s, star (f x)