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>

proc-macro/tests/balances.rs

@@ -30,10 +30,7 @@ use substrate_subxt::{
         MaybeSerialize,
         Member,
     },
-    system::{
-        System,
-        SystemEventsDecoder,
-    },
+    system::System,
     ClientBuilder,
     KusamaRuntime,
     PairSigner,