Use color management protocol on suitable PNG images

This is a minimal attempt at implementing https://github.com/swaywm/swaybg/issues/70. It: * Adds a -r/--render command line argument to specify the rendering intent for the image. * Only attempts color management for PNG images with a cICP chunk, and requires the compositor support exactly * Does not handle any of the other PNG color management chunks (mDCV, cLLI, sRGB, gAMA, cHRM) * Does not do color model aware blending (which would be another few hundred lines) * Does not support high bit depths * Does a blocking roundtrip whenever it commits a color managed surface All of these limitations can be fixed later.