Blender Git Loki

Fix #32603: Multi-Layer EXR files can't be color managed

Issue was caused by completely different way how multi-layer EXRs are loading,
they're bypassing general image buffer loading functions.

Solved by running color space transformation on render result construction
from multi-layer EXR image.

Also fixed issue with wrong display buffer computing for buffers with less
than 4 channels. Issues were:

- Display buffer is always expected to be RGBA
- OpenColorIO can not apply color space transformations on non-{RGB, RGBA}
pixels.