[tests] Add more matrix multiply tests

[epsilonError]

Added more tests for matrix multiply.
And utility functions so additional tests for multiply_v3_matrix3x3 will be easy to add.

The new tests are skipped, because they are provisional, and I just want to highlight them.
The expected results are still visible in the HTML runner version of the tests.

If these tests seem reasonable for generic matrix multiplication, I'd be happy to make minimal changes to multiplyMatrices that would pass these tests in a future pull request.

I have some broader questions around how matrix multiplication should work for color.js, but I started a discussion thread to have that broader conversation.

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[epsilonError]

I'll be adding a comment about my understanding of 'row-major ordered & pre-multiplication' vs 'column-major ordered & post-multiplication' to the broader discussion thread in the next few days.