[multiplyMatrices] Update implementation to pass all tests

[epsilonError]

Updates implementation and passes all tests for multiplyMatrices.

I attempted to make the smallest changes per commit to pass skipped tests. Once a test was passed, I didn't skip it again (resulting in one regression that was also fixed).

Note: To see that an error is no longer thrown by multiplying empty arrays, you'll have to comment out the

check: (..._args) => {
    return true; // Treat these tests as passed
},

block in the Incorrect Data test when running htest.

@lloydk, let me know how this looks to you. And I can also fit some refactoring into this pull request before it's merged, if needed.

I wanted to prioritize minimal changes to pass the tests which would make a future refactor easier to understand before I started it.

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[facelessuser]

I think the output generally looks okay to me. The results behave like I would expect. I do find the output in the HTML a bit frustrating as it strips all the brackets (which isn't something you are doing or can control). I would expect the multiplication of [[3]] and [[4]] to be [[12]], but the output strips all of that context when it is displayed and it looks like the scalar 12. So I assume it is being calculated with the appropriate dimensions, but I would have to checkout the commit locally to be sure. But generally, I think it looks good to me.