* Port over new code tables from Cycles
* Convert Rec.709 to scene linear for lookup table.
* Move code for wavelength and blackbody to IMB so they can access the
required transforms, which are not in blenlib.
* Remove clamping from blackbody shader to bypass the texture read.
Since it's variable now easiest to just always read from the texture
than pass additional parameters.
* Fold XYZ to RGB conversion into the wavelength table.
Ref T68926
This patch adds wavelength node support to Eevee, similar to how
Eevee Blackbody node works, thus it is a little off from Cycles.
Reviewed By: #eevee_viewport, fclem, brecht
Differential Revision: https://developer.blender.org/D11326
