1.38.2 Merge

[bernardkwok]

Major Changes:

• Patch id bumped to 1.38.2
• CM:
  • Update to new AcesCg 1.2 compliant names for default CM.
  • Fix implementations in OSL + MDL color management
• PBR:
  • Rational curve fit for GGX albedo
• Improvements to sheen rendering
• Shader translation:
  • Shader translation for SS->USDPreviewSurface example
• Web:
  • Python binding for ESSL shader
  • New "generateShader" Python utility. Includes ESSL generation.
  • Shader debug info added to browser test + changed zooming on viewer. Misc:
  • USDPreviewSurface UI tagging

Test results:

• Web browser test:
• RTS unit test (GLSL vs OSL) glsl_vs_osl.pdf
  • Sample comparison for procedural brick: