Fix invalid MeshRuntime::deformed_only for evaluated edit-meshes

Between 2.93 & 3.2 a regression was introduced where evaluated
meshes from the modifier stack would always have their deformed_only
value set to false.

Resolve by enabling for meshes returned by
BKE_mesh_wrapper_from_editmesh and ensure the value is kept when the
modifier duplicates the cage mesh.

Resolves #123138.

source/blender/blenkernel/intern/editmesh.cc

@@ -187,6 +187,10 @@ Span<float3> BKE_editmesh_vert_coords_when_deformed(
            (editmesh_eval_final->runtime->wrapper_type == ME_WRAPPER_TYPE_BMESH))
   {
     /* If this is an edit-mesh type, leave nullptr as we can use the vertex coords. */
+
+    /* If this is not empty, it's value should be assigned to `vert_positions`
+     * however the `mesh_cage` check above should handle this case. */
+    BLI_assert(BKE_mesh_wrapper_vert_coords(mesh_cage).is_empty());
   }
   else {
     /* Constructive modifiers have been used, we need to allocate coordinates. */

source/blender/blenkernel/intern/mesh_data_update.cc

@@ -858,6 +858,7 @@ static void editbmesh_calc_modifiers(Depsgraph &depsgraph,
       if (mesh_cage->runtime->edit_mesh) {
         mesh->runtime->edit_mesh = mesh_cage->runtime->edit_mesh;
         mesh->runtime->is_original_bmesh = true;
+        mesh->runtime->deformed_only = mesh_cage->runtime->deformed_only;
         if (mesh_cage->runtime->edit_data) {
           mesh->runtime->edit_data = std::make_unique<EditMeshData>(
               *mesh_cage->runtime->edit_data);

source/blender/blenkernel/intern/mesh_wrapper.cc

@@ -67,6 +67,9 @@ Mesh *BKE_mesh_wrapper_from_editmesh(std::shared_ptr<BMEditMesh> em,
   /* Use edit-mesh directly where possible. */
   mesh->runtime->is_original_bmesh = true;
 
+  /* Until the mesh is modified destructively it can be considered "deformed". */
+  mesh->runtime->deformed_only = true;
+
   mesh->runtime->edit_mesh = std::move(em);
 
   /* Make sure we crash if these are ever used. */