vo_gpu_next: linearize sRGB as a pure 2.2 power function

sRGB reference display is defined a 2.2 gamma device. To preserve the
look of the sRGB as mastered on such device, linearize it as such.

Note that sRGB encoding is piecewise with linear segment, which creates
mismatch to pure power 2.2 function, but this is intended to be viewed
on such display.

See:
IEC 61966-2-1-1999
https://community.acescentral.com/t/srgb-piece-wise-eotf-vs-pure-gamma/4024
https://github.com/KhronosGroup/DataFormat/issues/19
https://gitlab.freedesktop.org/pq/color-and-hdr/-/issues/12
https://github.com/dylanraga/win11hdr-srgb-to-gamma2.2-icm

DOCS/interface-changes/treat-srgb-as-power22.txt

@@ -0,0 +1 @@
+add `--treat-srgb-as-power22`