Add HDR Mod Compatibility

[rrtt217]

HDR Mod is a mod made by myself that enables native HDR output in Minecraft.

To correctly output in HDR, the following tasks must be done:

• Scaling and final output transform as in HDR Mod Wiki
• HDR compatible tonemaps:
  • GT and GT7
  • ACES Fit (another variant)
  • ACES Full
  • AgX (another varient by Allenwp, need to be tweaked for better SDR appearance)
  • Lottes (will need further parameter adjustment)

The following tasks are optimal for HDR, but not mandatory:

• Use RGBA16F buffer for colortex0/8 when HDR Mod is enabled (Macros in colortex*Format may affect compatibility)
• Generalize colorspace concept in code(e.g. not limiting working space to Rec.709)
• Refactor tonemapping-related code

[moyongxin]

We think we may consider some additional stuff:

• Generalize colorspaces(maybe an overhaul)
• Split tonemappers into different parts(display mappings and OOTFs. e.g. for all SDR tonemappers, use the same display mapping but different curves)

[rrtt217]

• As for genealizing colorspace, it requires some works to be done before the grading pass.
• Tonemappers except Lottes and ACES Full are already pure OOTF/display mapping/linearTolinear.
  • Lottes tonemapping used in Revelation is a variant of unknown origin with linearTosRGB baked in; using the original Lottes as OOTF is possible but requires more parameter tweaking.
  • As for ACES Full the tonemapper uses (and may targets at) bt.1886 w/ gamma 2.4 encoding, swiching to sRGB might slightly broken ACES Full.
  • The main problem is SDR tonemapper usually use a intrinsic maximum value of 1.0.