Calculate transform matrices at compile-time

[FreezyLemon]

src/yuv_rgb/color.rs has quite a bit of code that can logically be const-evaluated.

Basically, get_rgb_to_yuv_matrix and get_yuv_to_rgb_matrix (which is the first function plus 1 step) can be simplified into lookups of 3x3 matrices based only on the MatrixCoefficients and ColorPrimaries.

This could either be done by moving the calculation code into a build script (similar to this PR in ssimulacra2), or by using soft floats (e.g. const_soft_float and/or constgebra).

This could also allow removing the nalgebra dependency, since the only nalgebra code that really needs to run at runtime is the pix_vector * transform_matrix multiplication, which can be ported to a trivial helper function (because the dimensions are always the same).

[FreezyLemon]

Looks like 1.82 (currently beta) has stabilized some const floating point arithmetic: rust-lang/rust#128596.

Might be worth revisiting after stable release.

[FreezyLemon]

I've played around with this a bit and it looks like this won't be a real performance increase, maybe 1-2%. It could still be nice to ditch the nalgebra dependency... I've basically implemented this on my fork. It needs a bit of polishing, but the matrix stuff is ~200 lines of mostly boilerplate. I'll think about whether I want to open a PR with it.

[FreezyLemon]

Even when using const-evaluated LUTs, there doesn't seem to be a noteworthy performance increase. I think it's probably best to "just" ditch the nalgebra dependency by adding some Matrix boilerplate...