Instead of setting up a weird swizzle (which is linked to how the
internal renderer code works, rather than the generic format code), add
per-component mapping to gl_imgfmt_desc.
The renderer still computes the weird swizzle, but at least it's
confined to itself. Also, it appears the hwdec backends don't need this
anymore.
It's really nice that the messy init_format() goes away too.
The new API has literally no advantages (other than that we can drop
mp_vt_download_image and other things later), but it's sort-of uniform
with the other hwaccels.
"--videotoolbox-format=no" is not supported with the new API, because it
doesn't "fit in". Probably could be added later again.
The iOS code change is untested (no way to test).
Implements --hwdec=videotoolbox on iOS. Similar to hwdec_osx.c, but
using CVPixelBuffer APIs available on iOS instead of the equivalent
IOSurface APIs in macOS.
wm4
Aman Gupta