Configurable Config and Extra types (#373)

* WIP config

* WIP separate default config

* Separate trait impls on client

* WIP introduce new ApiConfig (to be renamed) trait

* Update generated polkadot codegen

* Allow configuring Config and Extra types independently

* Add extra default configuration

* Revert ir parsing of config attr

* Add default-features = false to substrate deps

* Revert "Add default-features = false to substrate deps"

This reverts commit 099d20cd4cbf8000ff938d1dc090ecbc28a5e788.

examples/polkadot_balance_transfer.rs

@@ -25,6 +25,8 @@
 use sp_keyring::AccountKeyring;
 use subxt::{
     ClientBuilder,
+    DefaultConfig,
+    DefaultExtra,
     PairSigner,
 };
 
@@ -41,7 +43,7 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
     let api = ClientBuilder::new()
         .build()
         .await?
-        .to_runtime_api::<polkadot::RuntimeApi<polkadot::DefaultConfig>>();
+        .to_runtime_api::<polkadot::RuntimeApi<DefaultConfig, DefaultExtra<DefaultConfig>>>();
     let hash = api
         .tx()
         .balances()