Make it so transform between color spaces which is a no-op does not
peroform any calculations.
This was initially found when working on #110941, but the issue can
be replicated easily by renaming "Linear" to "Linear Rec.709" and
adding alias as "Linear".
Doing so would result in a failure of the compositor_matte_test.
The reason for that is due to the image data-block still referring
to the "Linear" color space, the name-based comparison not detecting
that "Linear" and "Linear Rec.709" are the same spaces, and that the
cryptomatte requires bit-perfect floating point values.
Pull Request: https://projects.blender.org/blender/blender/pulls/110959
ba81908a2d