Remove the static supported_formats[] allowlist from hwcontext_cuda.
cuda_frames_get_constraints() now iterates all registered pixel formats
and includes every non-hwaccel, non-palette format. cuda_frames_init()
validates with av_pix_fmt_desc_get() instead of checking against the
allowlist.
Palette formats have a special-cased use of plane[1] for the palette itself
and it's not worth the hassle of supporting in an otherwise clean generic
copy loop.
Also add a roundtrip test that uploads a deterministic byte pattern to
CUDA, downloads it back, and verifies the data match. This tests all
non-hwaccel pixel formats. The test is gated on CONFIG_CUDA.
2cf3f4d64d