This is a bit more forward-facing than a bare allocation, and importantly,
allows the `swscale/utils.c` code to remain agnostic about how to correctly
uninit this struct.
Sponsored-by: Sovereign Tech Fund
Signed-off-by: Niklas Haas <git@haasn.dev>
AVFrame just really doesn't have the semantics we want. However, there a
tangible benefit to having SwsFrame act as a carbon copy of a (subset of)
AVFrame.
This partially reverts commit 67f3627267.
Sponsored-by: Sovereign Tech Fund
Signed-off-by: Niklas Haas <git@haasn.dev>
