Add helpful error message when using old type hint in shader language

[Kalrog]

• Adds an error message telling users to use source_color if they used hint_color in their code

[akien-mga]

There are more obsolete type hints than hint_color, so while this PR is useful in this specific case, it's missing a bunch of cases:

const char *RenamesMap3To4::shaders_renames[][2] = {
        { "ALPHA_SCISSOR", "ALPHA_SCISSOR_THRESHOLD" },
        { "CAMERA_MATRIX", "INV_VIEW_MATRIX" },
        { "INV_CAMERA_MATRIX", "VIEW_MATRIX" },
        { "NORMALMAP", "NORMAL_MAP" },
        { "NORMALMAP_DEPTH", "NORMAL_MAP_DEPTH" },
        { "TRANSMISSION", "BACKLIGHT" },
        { "WORLD_MATRIX", "MODEL_MATRIX" },
        { "depth_draw_alpha_prepass", "depth_prepass_alpha" },
        { "hint_albedo", "source_color" },
        { "hint_aniso", "hint_anisotropy" },
        { "hint_black", "hint_default_black" },
        { "hint_black_albedo", "hint_default_black" },
        { "hint_color", "source_color" },
        { "hint_white", "hint_default_white" },
        { nullptr, nullptr },
};

Maybe it could use the above map directly (from editor/renames_map_3_to_4.cpp).

One issue though is architectural, shader_language.cpp is part of servers / the runtime and should normally not depend on editor code. This could still be added with proper #if defined(TOOLS_ENABLED) && !defined(DISABLE_DEPRECATED) guards, but it would be a breach of our guidelines: #53295.

GDScript does it though:

godot/modules/gdscript/gdscript_analyzer.cpp

Lines 47 to 50 in 75e0b90

	#if defined(TOOLS_ENABLED) && !defined(DISABLE_DEPRECATED)
	#define SUGGEST_GODOT4_RENAMES
	#include "editor/renames_map_3_to_4.h"
	#endif

If we could handle this in the shader editor code directly, that would be best, but otherwise doing it like GDScript might be acceptable even if it's breaks encapsulation slightly (technically this editor/renames_map_3_to_4.h header file doesn't really depend on editor-specific stuff, so we could even move it to core if that was really a problem - but I wouldn't suggest doing that in this PR).