Test the five public functions not already covered by
tests/color_utils: av_csp_luma_coeffs_from_avcsp,
av_csp_primaries_desc_from_id, av_csp_primaries_id_from_desc,
av_csp_approximate_trc_gamma, and av_csp_approximate_eotf_gamma.
Iterates every AVCOL_SPC, AVCOL_PRI, and AVCOL_TRC value including
the extended ranges, round-trips primaries via desc_eq so the
canonical first-match (e.g. smpte170m for smpte240m) is accepted,
checks that a garbage desc returns AVCOL_PRI_UNSPECIFIED, and that
out-of-range enum values return NULL or 0.0 as documented. The
trc/eotf gamma values come from static lookup tables so the
floating point output is bitexact across platforms.
Coverage for libavutil/csp.c: 88.50% -> 94.46%
marcos ashtonandmichaelni
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