[Radiance] Refactor Cortex API classes to something a bit more commonly named

[kirill-grouchnikov]

Right now there are four configuration classes in Radiance:

• NeonCortex
• TridentCortex
• SubstanceCortex
• SubstanceExtrasCortex

After the big refactoring and unification scheduled for Heliotrope is done, it is time to reconsider the naming of these classes to something a bit more conventional.

[kirill-grouchnikov]

Removing from 6.0 as it already has enough breaking changes.