Fix #135159: Copied modifier doesn't keep the name of the modifier

`BKE_modifier_copy_ex` did it (which is called e.g. when copying the
whole stack from one object to another), but when simply duplicating a
modifier (`modifier_copy`), it was just ensuring a unique name (based on
the default name) without copyig the existing name prior.

Pull Request: https://projects.blender.org/blender/blender/pulls/135172

source/blender/editors/object/object_modifier.cc

@@ -1640,6 +1640,7 @@ bool modifier_copy(
   ModifierData *nmd = BKE_modifier_new(md->type);
   BKE_modifier_copydata(md, nmd);
   BLI_insertlinkafter(&ob->modifiers, md, nmd);
+  STRNCPY(nmd->name, md->name);
   BKE_modifier_unique_name(&ob->modifiers, nmd);
   BKE_modifiers_persistent_uid_init(*ob, *nmd);
   BKE_object_modifier_set_active(ob, nmd);