Project matmul complexity

[Bihaqo]

Change the order of lhs and rhs einsums to
(1, 2, 0, 3), 'aikd,sabc,bije,scjkf->sdef'
and
(1, 2, 0, 3), 'cikf,sdef,bije,sajkd->sabc'

and change the complexity to
O(d R n r2 ry s + d R n r ry2 s + d R2 n2 r ry s)
or
O(d R2 n2 r ry s) given that both r and ry are < Rn

[Bihaqo]

#166