Root ComActivator for hosting (#54524)

* rooting ComActivator that is needed for hosting

* FB

Author: LakshanF

src/coreclr/System.Private.CoreLib/src/ILLink/ILLink.Descriptors.Windows.xml

@@ -4,5 +4,11 @@
     <type fullname="System.Runtime.InteropServices.IDispatch" />
     <type fullname="System.Runtime.InteropServices.IMarshal" />
     <type fullname="Internal.Runtime.InteropServices.IClassFactory2" />
+    <!-- ComActivator is needed for native host operations -->
+    <type fullname="Internal.Runtime.InteropServices.ComActivator" >
+      <method name="GetClassFactoryForTypeInternal" />
+      <method name="RegisterClassForTypeInternal" />
+      <method name="UnregisterClassForTypeInternal" />
+    </type>
   </assembly>
 </linker>