Split and reduce SVD test sizes.

The original tests consume A LOT of memory - causing MSVC to constantly run out of heap space, gcc to sometimes crash without warning, and our CI machines to start using swap space, drastically slowing down compile times.

Here we split up and re-number a bunch of the tests. Also reduced some fixed-size matrix sizes - the new stack allocation for U/V gets pretty big, which also seems to be drastically slowing down compile times.