Always send lights to sky shader if using sun scatter

[Kaleb-Reid]

Currently sun scatter isn't applied to the sky properly if the sky shader doesn't contain any LIGHTX_* built-ins.

Fixes #107924.

[clayjohn]

Do you know why this isn't needed with the compatibility renderer? the code appears to be the same

[Kaleb-Reid]

@clayjohn I actually went back and tested again and you're right to question why this doesn't happen in Compatibility because it does have a similar problem which I've now fixed.

godot/drivers/gles3/rasterizer_scene_gles3.cpp

Lines 687 to 688 in 987832b

	if (shader_data->uses_light) {
	sky_globals.directional_light_count = 0;

In the Compatibility renderer the light count only gets set to 0 in the sky if the shader uses any of the LIGHTX_* built-ins, so if you add a light while you have a sky which uses them and then remove all of the built-ins the sun scatter stays but does not update if you modify the lights.

[clayjohn]

Looks great!

[Kaleb-Reid]

@clayjohn I made a minor change: updating the lights solely for sun scatter should probably also check if fog is enabled. I'm not sure if you need to approve this again or how that side of things works.

[clayjohn]

Thanks for letting me know. I usually approve again in these situations.

[Repiteo]

Thanks!