This is in prevision of EEVEE panoramic projection support.
EEVEE-Next is planned to add support for these parameters.
Not having these parameters in Blender DNA will make Cycles
and EEVEE not share the same parameters and will be confusing
for the user.
We handle forward compatibility by still writing the parameters
as ID properties as previous cycles versions expect.
Since this change will break the API compatibility it is crucial
to make it for the 4.0 release.
Related Task #109639
Pull Request: https://projects.blender.org/blender/blender/pulls/111310
Clément Foucault
acd6dd96b7