[Feature] Understand how and where gamma and color spaces should appear in the pipeline.

[Adnn]

In particular, the question of gamma correction is raised by FreeType, and might impact Texting renderer blending.

For optimal rendering on a screen the bitmap should be used as an alpha channel in linear blending with gamma correction.

In particular, FreeType doc mentions converting from sRGB space to linear space before blending, which raises questions:

• Are we not already working in linear color space anyway?
  • If so, should gamma correction only be applied once as a post processing pass?