Track IObservableMap<K,V> Impl type in the interop generator

The IObservableMap2 Impl builder created the Impl type but never registered it
via emitState.TrackTypeDefinition (unlike IObservableVector1, IList1, IDictionary2,
etc.). As a result, a user-defined type implementing IObservableMap<K,V> (e.g.
ObservableDictionary) failed CCW/vtable generation with CSWINRTINTEROPGEN0024
(Impl lookup miss) wrapped as CSWINRTINTEROPGEN0039. Track it like the other
collection Impl builders.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: manodasanW

src/WinRT.Interop.Generator/Builders/InteropTypeDefinitionBuilder.IObservableMap2.cs

@@ -531,6 +531,9 @@ public static void ImplType(
             implType.Methods.Add(makeMapChangedMethod);
             implType.Methods.Add(get_MapChangedTableMethod);
             implType.Properties.Add(mapChangedTableProperty);
+
+            // Track the type (it may be needed by COM interface entries for user-defined types)
+            emitState.TrackTypeDefinition(implType, mapType, "Impl");
         }
     }
 }