start fixing examples and cleaning up interface

subxt/examples/setup_client_offline.rs

@@ -16,7 +16,7 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
     };
 
     // 2. A runtime version (system_version constant on a Substrate node has these):
-    let runtime_version = subxt::backend::RuntimeVersion {
+    let runtime_version = subxt_core::RuntimeVersion {
         spec_version: 9370,
         transaction_version: 20,
     };