Preserved block and boundary names of secondary meshes in CombinerGen…

…erator

Closes idaholab#22838

framework/doc/content/source/meshgenerators/CombinerGenerator.md

@@ -6,6 +6,12 @@
 
 The `CombinerGenerator` allows the user to combine the outputs of multiple `MeshGenerator`s into a single mesh.  This is somewhat similar to the [StitchedMeshGenerator.md] with the difference being that `CombinerGenerator` makes no attempt to "heal" / "join" the mesh like [StitchedMeshGenerator.md] does.  There `CombinerGenerator` is more suited to creation of disjoint meshes (where the individual pieces are not directly tied together).
 
+!alert note title=Mesh naming precedence
+`CombinerGenerator` preserves subdomain names and boundary names (node sets, side sets, and edge sets).
+If the corresponding IDs exist in multiple meshes, then the meshes/copies listed
+later in [!param](/Mesh/CombinerGenerator/inputs)/[!param](/Mesh/CombinerGenerator/positions)
+take precedence.
+
 ## Usage
 
 There are three main ways to use the `CombinerGenerator`:

framework/src/meshgenerators/CombinerGenerator.C

@@ -252,6 +252,15 @@ CombinerGenerator::copyIntoMesh(UnstructuredMesh & destination, const Unstructur
   for (const auto & t : other_boundary.build_shellface_list())
     boundary.add_shellface(std::get<0>(t) + elem_delta, std::get<1>(t), std::get<2>(t));
 
+  for (auto elem : source.get_subdomain_name_map())
+    destination.set_subdomain_name_map().insert(elem);
+
+  for (auto elem : other_boundary.get_nodeset_name_map())
+    boundary.set_nodeset_name_map().insert(elem);
+
   for (auto elem : other_boundary.get_sideset_name_map())
     boundary.set_sideset_name_map().insert(elem);
+
+  for (auto elem : other_boundary.get_edgeset_name_map())
+    boundary.set_edgeset_name_map().insert(elem);
 }