GPv3: Show Line Art options in object add menu

Now Add->Grease Pencil menu will show Scene/Collection/Object line art
options.

@@ -1289,4 +1289,18 @@ void create_suzanne(Main &bmain, Object &object, const float4x4 &matrix, const i
   drawing_fills.tag_topology_changed();
 }
 
+void create_blank_for_lineart(Main &bmain, Object &object, const int frame_number)

@@ -1669,0 +1678,4 @@
+      const int stroke_depth_order = RNA_enum_get(op->ptr, "stroke_depth_order");
+      const float stroke_depth_offset = RNA_float_get(op->ptr, "stroke_depth_offset");
+
+      float radius = RNA_float_get(op->ptr, "radius");

@@ -1669,0 +1679,4 @@
+      const float stroke_depth_offset = RNA_float_get(op->ptr, "stroke_depth_offset");
+
+      float radius = RNA_float_get(op->ptr, "radius");
+      float scale[3];

@@ -1669,0 +1683,4 @@
+      copy_v3_fl(scale, radius);
+      float mat[4][4];
+
+      ED_object_new_primitive_matrix(C, object, loc, rot, scale, mat);

@@ -1669,0 +1702,4 @@
+        md->source_type = LINEART_SOURCE_SCENE;
+      }
+      /* Only created one layer and one material. */
+      STRNCPY(md->target_layer, grease_pencil->layers()[0]->name().c_str());

@@ -1669,0 +1703,4 @@
+      }
+      /* Only created one layer and one material. */
+      STRNCPY(md->target_layer, grease_pencil->layers()[0]->name().c_str());
+      md->target_material = grease_pencil->material_array[0];

@@ -1669,0 +1721,4 @@
+      }
+      else {
+        if (stroke_depth_order == GP_DRAWMODE_3D) {
+          /* gpd->draw_mode = GP_DRAWMODE_3D; */