Request true floating-point EGL configs for scRGB and expose the native
encodings supported by the selected surface. Fall back to software HDR
mapping when the surface cannot represent the incoming wire format.
Resample PQ in linear light, keep SDR-only effects out of native PQ
chains, and consume the cursor-specific white level without changing
binary monochrome cursor mask operations.
This fixes a rounding issue on certain hardware (NVidia) which actually
implement mediump as half precision (16-bit) float. It's safe to assume
`highp` is available as if the GPU does not support it, then the shader
compiler will try to find a lower precision that is supported by the GPU
