Blender Git Loki

Fix channel packed images display in the Image/Node editor

Channel packed images should not have their RGB affected by alpha.
rendering in Cycles and Eevee was fine already, but displaying these was
not right in the Image and Node editors.

Not 100% sure what to do for the "Color and Alpha" mode, but I guess
this should stay like it was before (applying the alpha).

"Color", "R", "G", and "B" modes were changed to not have color be
affected by alpha though.

ref. T89034

Maniphest Tasks: T89034

Differential Revision: https://developer.blender.org/D11871