fix lstrip in biguint (#6151)

* add failing test for multiply_by_rational

* fix BigUint

* fix length

* bump version

* merge tests

substrate/bin/node/runtime/src/lib.rs

@@ -94,7 +94,7 @@ pub const VERSION: RuntimeVersion = RuntimeVersion {
 	// implementation changes and behavior does not, then leave spec_version as
 	// is and increment impl_version.
 	spec_version: 251,
-	impl_version: 0,
+	impl_version: 1,
 	apis: RUNTIME_API_VERSIONS,
 	transaction_version: 1,
 };