The Cryptomatte layers in the compositor are saved compressed and saved
in half precision in the File Output node. That's because the EXR writer
makes decision about compression and half float based on channel names.
And Cryptomatte are currently saved using RGBA channel names like other
color images.
To fix this, we follow the Cycles convention of using lowercase rgba for
Cryptomatte images, allowing them to be saved without compression and
always in full precision since they are otherwise useless.
Fixes#124208, #87988.
Pull Request: https://projects.blender.org/blender/blender/pulls/124508
d14ad05078