feat(data/matrix/kronecker): add two lemmas (#8700)
Added two lemmas `kronecker_map_assoc` and `kronecker_assoc` showing associativity of the Kronecker product
Co-authored-by: Filippo A. E. Nuccio <65080144+faenuccio@users.noreply.github.com>
Co-authored-by: Eric Wieser <wieser.eric@gmail.com>
