mathlib3

909b6732 - split(data/set/semiring): Split off `data.set.pointwise` (#14145)

split(data/set/semiring): Split off `data.set.pointwise` (#14145) Move `set_semiring` to a new file `data.set.semiring`. Crediting Floris for #3240 Co-authored-by: Eric Wieser <wieser.eric@gmail.com>