XCM ExportMessage benchmark support (#6923)

* XCM ExportMessage benchmark support

* include inner-xcm in ExportMessage benchmark

---------

Signed-off-by: acatangiu <adrian@parity.io>

polkadot/runtime/kusama/src/lib.rs

@@ -2107,6 +2107,12 @@ sp_api::impl_runtime_apis! {
 					// Kusama doesn't support asset locking
 					Err(BenchmarkError::Skip)
 				}
+
+				fn export_message_origin_and_destination(
+				) -> Result<(MultiLocation, NetworkId, InteriorMultiLocation), BenchmarkError> {
+					// Kusama doesn't support exporting messages
+					Err(BenchmarkError::Skip)
+				}
 			}
 
 			let whitelist: Vec<TrackedStorageKey> = vec![

polkadot/runtime/kusama/src/weights/xcm/mod.rs

@@ -243,7 +243,8 @@ impl<RuntimeCall> XcmWeightInfo<RuntimeCall> for KusamaXcmWeight<RuntimeCall> {
 		Weight::MAX
 	}
 	fn export_message(_: &NetworkId, _: &Junctions, _: &Xcm<()>) -> Weight {
-		Weight::MAX // todo fix
+		// Kusama relay should not support export message operations
+		Weight::MAX
 	}
 	fn lock_asset(_: &MultiAsset, _: &MultiLocation) -> Weight {
 		// Kusama does not currently support asset locking operations