Add EXT_sRGB_write_control (host side)

This series enabled host support for EXT_sRGB_write_control needed to support and pass the tests

dEQP-GLES31.functional.fbo.srgb_write_control.framebuffer_srgb_enabled*

The guest/mesa side requirements are in the works in this branch:

https://gitlab.collabora.com/virgl-es/mesa/tree/add-EXT_sRGB_write_control

v2: Instead of using a CAP to communicate the support for the extension use support for PIPE_FORMAT_B8G8R8A8_SRGB to signal the guest - it is supported on D-GL and not required but possible to provide on GLES.

v3: rework the patches and correct border color handling for emulated BGRA_sRGB format