Fix mat * vec with non-commutative numbers

[jishnub]

This now matches LinearAlgebra's convention of A * B * alpha + C * beta, from the current alpha * A * B + beta * C.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (e445b49) 89.55% compared to head (804a937) 89.55%.
Report is 3 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #413   +/-   ##
=======================================
  Coverage   89.55%   89.55%           
=======================================
  Files          25       25           
  Lines        3542     3544    +2     
=======================================
+ Hits         3172     3174    +2     
  Misses        370      370           

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