Fix codegen validation when Runtime APIs are stripped (#1000)

* modify code gen

* cargo fmt

* fix return

* move the runtime_apis static

* small layout change

* tidy up metadata UI testing and test validation function too

* fix validation tests to point to metadata

* update codegen

* fix clippy and tests

* tweak a comment

* rename validate_codegen => is_codegen_valid_for

---------

Co-authored-by: James Wilson <james@jsdw.me>

subxt/src/metadata/metadata_type.rs

@@ -59,6 +59,13 @@ impl From<subxt_metadata::Metadata> for Metadata {
     }
 }
 
+impl TryFrom<frame_metadata::RuntimeMetadataPrefixed> for Metadata {
+    type Error = subxt_metadata::TryFromError;
+    fn try_from(value: frame_metadata::RuntimeMetadataPrefixed) -> Result<Self, Self::Error> {
+        subxt_metadata::Metadata::try_from(value).map(Metadata::from)
+    }
+}
+
 impl codec::Decode for Metadata {
     fn decode<I: codec::Input>(input: &mut I) -> Result<Self, codec::Error> {
         subxt_metadata::Metadata::decode(input).map(Metadata::new)