Enable depth writes during shadow pass and depth pass. Disable during color pass

This fixes an unreported performance bug. Basically, without this change, the depth prepass did nothing

(cherry picked from commit b986afed4658def08447516c9ca66e17e1cbc970)

drivers/gles3/rasterizer_scene_gles3.cpp

@@ -2166,7 +2166,9 @@ void RasterizerSceneGLES3::_render_list_template(RenderListParameters *p_params,
 		if (scene_state.current_depth_draw != shader->depth_draw) {
 			switch (shader->depth_draw) {
 				case GLES3::SceneShaderData::DEPTH_DRAW_OPAQUE: {
-					glDepthMask(p_pass_mode == PASS_MODE_COLOR);
+					glDepthMask((p_pass_mode == PASS_MODE_COLOR && !GLES3::Config::get_singleton()->use_depth_prepass) ||
+							p_pass_mode == PASS_MODE_DEPTH ||
+							p_pass_mode == PASS_MODE_SHADOW);
 				} break;
 				case GLES3::SceneShaderData::DEPTH_DRAW_ALWAYS: {
 					glDepthMask(GL_TRUE);