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

examples/wasm-example/src/services.rs

@@ -49,7 +49,6 @@ pub(crate) async fn subscribe_to_finalized_blocks(
         writeln!(output, "  Extrinsics:").ok();
         let extrinsics = block.extrinsics().await?;
         for ext in extrinsics.iter() {
-            let ext = ext?;
             let idx = ext.index();
             let events = ext.events().await?;
             let bytes_hex = format!("0x{}", hex::encode(ext.bytes()));