Add property hint for 2D shadow size project setting

Previously, it was possible to use zero or negative values, which are
invalid.

This also prevents crashing the engine by setting a shadow size of
0 or lower from a script.

servers/rendering/renderer_rd/renderer_canvas_render_rd.cpp

@@ -2759,7 +2759,7 @@ bool RendererCanvasRenderRD::free(RID p_rid) {
 }
 
 void RendererCanvasRenderRD::set_shadow_texture_size(int p_size) {
-	p_size = nearest_power_of_2_templated(p_size);
+	p_size = MAX(1, nearest_power_of_2_templated(p_size));
 	if (p_size == state.shadow_texture_size) {
 		return;
 	}

servers/rendering_server.cpp

@@ -3345,7 +3345,7 @@ void RenderingServer::init() {
 	GLOBAL_DEF(PropertyInfo(Variant::INT, "rendering/lights_and_shadows/positional_shadow/soft_shadow_filter_quality", PROPERTY_HINT_ENUM, "Hard (Fastest),Soft Very Low (Faster),Soft Low (Fast),Soft Medium (Average),Soft High (Slow),Soft Ultra (Slowest)"), 2);
 	GLOBAL_DEF("rendering/lights_and_shadows/positional_shadow/soft_shadow_filter_quality.mobile", 0);
 
-	GLOBAL_DEF("rendering/2d/shadow_atlas/size", 2048);
+	GLOBAL_DEF(PropertyInfo(Variant::INT, "rendering/2d/shadow_atlas/size", PROPERTY_HINT_RANGE, "128,16384"), 2048);
 
 	// Number of commands that can be drawn per frame.
 	GLOBAL_DEF_RST(PropertyInfo(Variant::INT, "rendering/gl_compatibility/item_buffer_size", PROPERTY_HINT_RANGE, "128,1048576,1"), 16384);