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

core/src/config/transaction_extensions.rs

@@ -587,7 +587,7 @@ macro_rules! impl_tuples {
                 // there is one, and add it to a map with that index as the key.
                 let mut exts_by_index = HashMap::new();
                 $({
-                    for (idx, e) in metadata.extrinsic().transaction_extensions().iter().enumerate() {
+                    for (idx, e) in metadata.extrinsic().transaction_extensions_to_use_for_encoding().enumerate() {
                         // Skip over any exts that have a match already:
                         if exts_by_index.contains_key(&idx) {
                             continue
@@ -604,7 +604,7 @@ macro_rules! impl_tuples {
 
                 // Next, turn these into an ordered vec, erroring if we haven't matched on any exts yet.
                 let mut params = Vec::new();
-                for (idx, e) in metadata.extrinsic().transaction_extensions().iter().enumerate() {
+                for (idx, e) in metadata.extrinsic().transaction_extensions_to_use_for_encoding().enumerate() {
                     let Some(ext) = exts_by_index.remove(&idx) else {
                         if is_type_empty(e.extra_ty(), types) {
                             continue