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! {

codegen/src/api/runtime_apis.rs

@@ -33,7 +33,7 @@ fn generate_runtime_api(
         .then_some(quote! { #( #[doc = #docs ] )* })
         .unwrap_or_default();
 
-    let structs_and_methods: Vec<_> = api
+    let structs_and_methods = api
         .methods()
         .map(|method| {
             let method_name = format_ident!("{}", method.name());
@@ -126,13 +126,7 @@ fn generate_runtime_api(
                 }
             );
 
-            let Some(call_hash) = api.method_hash(method.name()) else {
-                return Err(CodegenError::MissingRuntimeApiMetadata(
-                    trait_name_str.to_owned(),
-                    method_name_str.to_owned(),
-                ))
-            };
-
+            let call_hash = method.hash();
             let method = quote!(
                 #docs
                 pub fn #method_name(&self, #( #fn_params, )* ) -> #crate_path::runtime_api::payload::StaticPayload<types::#struct_name, types::#method_name::output::Output> {
@@ -147,7 +141,7 @@ fn generate_runtime_api(
 
             Ok((struct_input, method))
         })
-        .collect::<Result<_, _>>()?;
+        .collect::<Result<Vec<_>, CodegenError>>()?;
 
     let trait_name = format_ident!("{}", trait_name_str);