gpu: entirely refactor pl_gpu_caps

I wasn't happy with this bit field. It was clumsy, interfered with rebases, limited to 64 entries, awkward to work with, and didn't really serve any practical purpose.

Additionally, a lot of these fields make far more sense in pl_glsl_desc rather than pl_gpu_limits, especially the ones that only affect shader generation, as these are also useful for pl_shader.

The various blacklist_caps fields were deleted without a deprecation because I don't think they had any users other than our own CI.