Add hooks to register event types for decoding (#227)

* Global registration of type segmenters for event decoding

* Perform type sizes check when building client

* Introduce EventTypeRegistry for global runtime type sizes

* Fmt

* Register runtime type sizes on creation of EventTypeRegistry

* Register more default dispatch types

* Add missing type sizes

* fmt

* Fix up register_type_size builder method

* Update doc comments

* Make register_default_type_sizes public

* Don't allow duplicate registered types

* Remove call to supertraits type registration, done manually in Runtime

* Fix tests and warnings

* Fix duplicate type registration

* Fmt

* review: use is_empty()

Co-authored-by: Niklas Adolfsson <niklasadolfsson1@gmail.com>

* Add panic docs

Co-authored-by: Niklas Adolfsson <niklasadolfsson1@gmail.com>

examples/transfer_subscribe.rs

@@ -17,7 +17,6 @@
 use sp_keyring::AccountKeyring;
 use substrate_subxt::{
     balances::{
-        BalancesEventsDecoder,
         TransferCallExt,
         TransferEvent,
     },
@@ -25,7 +24,6 @@ use substrate_subxt::{
     ClientBuilder,
     DefaultNodeRuntime,
     EventSubscription,
-    EventsDecoder,
     PairSigner,
 };
 
@@ -38,8 +36,7 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
 
     let client = ClientBuilder::<DefaultNodeRuntime>::new().build().await?;
     let sub = client.subscribe_events().await?;
-    let mut decoder = EventsDecoder::<DefaultNodeRuntime>::new(client.metadata().clone());
-    decoder.with_balances();
+    let decoder = client.events_decoder();
     let mut sub = EventSubscription::<DefaultNodeRuntime>::new(sub, decoder);
     sub.filter_event::<TransferEvent<_>>();
     client.transfer(&signer, &dest, 10_000).await?;