Support V16 metadata and refactor metadata code (#1967)

* WIP integrate unstable v16 metadata into Subxt

* first pass moving retain to the CLI tool

* Remove otuer enum variant stripping and move now simpler strip_metadata to new crate. test it

* tidyup to use stripmetadata package etc

* Fix / comment out tests

* fmt

* clippy

* Fix wasm example

* wasm-example fix

* wasm-example fix

* Maske sure to move IDs around after types.retain()

* fmt

* Tweak comment

* Find dispatch error separately to avoid issues during mapping

* Expose associated type information in pallet metadata

* Hopefully fix flaky archive RPC

* remove unwanted temp file

* Address nits

* Add back commented-otu tests and address review comments

* use either, and simplify for_each

codegen/src/api/mod.rs

@@ -157,8 +157,6 @@ impl RuntimeGenerator {
             .collect();
         let runtime_api_names_len = runtime_api_names.len();
 
-        let metadata_hash = self.metadata.hasher().hash();
-
         let modules = pallets_with_mod_names
             .iter()
             .map(|(pallet, mod_name)| {
@@ -219,7 +217,6 @@ impl RuntimeGenerator {
 
         // Fetch the paths of the outer enums.
         // Substrate exposes those under `kitchensink_runtime`, while Polkadot under `polkadot_runtime`.
-
         let call_path = type_gen
             .resolve_type_path(self.metadata.outer_enums().call_enum_ty())?
             .to_token_stream(type_gen.settings());
@@ -230,6 +227,8 @@ impl RuntimeGenerator {
             .resolve_type_path(self.metadata.outer_enums().error_enum_ty())?
             .to_token_stream(type_gen.settings());
 
+        let metadata_hash = self.metadata.hasher().hash();
+
         let custom_values = generate_custom_values(&self.metadata, &type_gen, &crate_path);
 
         Ok(quote! {