Rename hint_albedo, hint_white/black in shaders

[Chaosus]

Approved changes from PR meeting (godotengine/godot-proposals#2323 (comment)):

• hint_albedo/hint_black_albedo/hint_color → source_color
• hint_black/hint_white → hint_default_black/hint_default_white

Closes godotengine/godot-proposals#2323

[clayjohn]

Although not mentioned in the comment, the plan was also to replace hint_color with source_color.

[Chaosus]

@clayjohn hint_albedo already has been renamed to source_color, to what rename of hint_color?

[clayjohn]

They should both be renamed to source_color

[Chaosus]

@clayjohn Done. Check if you want.

[akien-mga]

Thanks!

[GiantBlargg]

The replacement for hint_black_albedo, source_color, hint_default_black doesn't work, as the uniform only stores the most recent hint.

Hint is overwritten here: https://github.com/Chaosus/godot/blob/a8bbe570caadd0161a8db9c980296b111042a6b8/servers/rendering/shader_language.cpp#L8235-L8262

[Chaosus]

@GiantBlargg Thanks for the notice - but next time create a new issue instead of posting to the closed PR. This should be fixed by #61554