Fix a default shader specular render mode to SCHLICK_GGX

[Chaosus]

Makes shader pipeline use SPECULAR_SCHLICK_GGX(desktop) and SPECULAR_BLINN(mobile) - parameter by default (and if the user didn't define render_mode directly).

revert #41533

Bugsquad edit: Fixes #46838.

[reduz]

I would really prefer to not add so much stuff in the shaders, what was the original problem?

[Chaosus]

what was the original problem?

#46838

[BastiaanOlij]

I would be fine with the change as shown, my only remark was that the setting between GGX/BLINN was over kill so I am happy with the current solution to make GGX the default on desktop and BLINN the default on mobile. The check at the top of the shader makes it very clear to anyone reading the code what the desired behavior is.

Do need to make sure this is properly documented.

[Calinou]

I would be fine with the change as shown, my only remark was that the setting between GGX/BLINN was over kill so I am happy with the current solution to make GGX the default on desktop and BLINN the default on mobile.

According to #22637, Blinn could be removed entirely since GGX has the same number of instructions. Maybe Phong should be removed too, I'm not sure.

[Chaosus]

@Calinou Ok changed to schilck in both cases.

[clayjohn]

As a note to whoever merges this #46838 is a 3.x issue and should not be closed by this PR.

[akien-mga]

Thanks!