Blender Git Loki

Fix T93090: crash with data transfer modifier and geometry nodes

There was a missing normals layer that was requested by the data transfer
modifier from the target object. The normal layer was correctly added to
the target object. However, it never reached the data transfer modifier
because the mesh was copied in `BKE_object_get_evaluated_mesh`
(in the call to `get_mesh_for_write`) and the copy does not include the normals
layer.

The solution is to not use `get_mesh_for_write` here which was only used
because `BKE_object_get_evaluated_mesh` returns a non-const `Mesh *`.
Mid term, it should actually return a `const Mesh *` to avoid the confusion.

Differential Revision: https://developer.blender.org/D13319