Allow more efficient marshalling to IDispatch (dotnet#53065)

In NativeAOT scenario this allow to not rely on reflection to get GUID of the IDispatch, since it is well known. 
Related to dotnet/runtimelab#1142

Author: kant2002

src/libraries/Common/src/System/Runtime/InteropServices/Variant.cs

@@ -202,7 +202,7 @@ public unsafe void CopyFromIndirect(object value)
                     break;
 
                 case VarEnum.VT_DISPATCH:
-                    *(IntPtr*)this._typeUnion._unionTypes._byref = Marshal.GetComInterfaceForObject<object, IDispatch>(value);
+                    *(IntPtr*)this._typeUnion._unionTypes._byref = Marshal.GetIDispatchForObject(value);
                     break;
 
                 case VarEnum.VT_BSTR:
@@ -698,7 +698,7 @@ public object? AsDispatch
                 }
                 else
                 {
-                    _typeUnion._unionTypes._dispatch = Marshal.GetComInterfaceForObject<object, IDispatch>(value);
+                    _typeUnion._unionTypes._dispatch = Marshal.GetIDispatchForObject(value);
                 }
             }
         }