Add standard divide and conquer matrix multiplication test for comparison.

3 jobs from master in 4 minutes 13 seconds (queued for 1 second)
Status Job ID Name Coverage
  Build
passed #3843
build_cmake

01:03

 
  Test
passed #3844
run_tests

01:06

 
  Sanitizer
passed #3845
run_address_sanitizer

02:03