Use frame-decode for core extrinsic decode logic (#1785)

* WIP using frame-decode for core extrinsic decode logic

* fmt

* Fix dependabot config

* clippy

* tidy some imports

* Fix a couple of tests

* Update to frame-decode 0.0.7

* fix docs

* Decode exts earlier to avoid doing it every iter/find step

* frame-decode to 0.1.0

* fmt

* clippy

* fix wasm example

* doc test fixes

* Fix test

* Fix a couple of subxt_core tests

testing/integration-tests/src/full_client/client/unstable_rpcs.rs

@@ -367,10 +367,7 @@ async fn transaction_v1_broadcast() {
         }
 
         let extrinsics = finalized.extrinsics().await.unwrap();
-        let block_extrinsics = extrinsics
-            .iter()
-            .map(|res| res.unwrap())
-            .collect::<Vec<_>>();
+        let block_extrinsics = extrinsics.iter().collect::<Vec<_>>();
 
         let Some(ext) = block_extrinsics
             .iter()