Improves tree and ground tile appearance

Refactors tree spawning and rendering:
- Adds seasonal color variations for trees via scripts.
- Introduces `ColorStorage` to manage tree and grass colors
- Removes unused code from tree spawning logic.
- Adjusts ground tile color for better visual appeal.
- Hides debug text on ground tiles.

falloff.gdshader

@@ -0,0 +1,10 @@
+shader_type canvas_item;
+
+uniform sampler2D gradient_fallof;
+
+void light() {
+	float calculated_light_value = max(0.0, dot(NORMAL, LIGHT_DIRECTION));
+	float sample = clamp(calculated_light_value * LIGHT_ENERGY, 0.05, 0.95);
+	vec4 shaded_texture = texture(gradient_fallof, vec2(sample, 0));
+	LIGHT = vec4(LIGHT_COLOR.rgb * COLOR.rgb * shaded_texture.rgb, LIGHT_COLOR.a);
+}