Use the generated DispatchError instead of the hardcoded Substrate one (#394)

* WIP DispatchError generic param

* main crate now compiling with new E generic param for DispatchError

* Remove E param from RpcClient since it doesn't really need it

* Point to generated DispatchError in codegen so no need for additional param there

* More error hunting; cargo check --all-targets passes now

* Use our own RuntimeVersion struct (for now) to avoid error decoding into sp_version::RuntimeVersion

* cargo fmt

* fix docs and expose private documented thing that I think should be pub

* move error info to compile time so that we can make DispatchError a little nicer to work with

* cargo fmt

* clippy

* Rework error handling to remove <E> param in most cases

* fix Error doc ambiguity (hopefully)

* doc tweaks

* docs: remove dismbiguation thing that isn't needed now

* One more Error<E> that can be a BasicError

* rewrite pallet errors thing into normal loops to tidy

* tidy errors codegen a little

* tidy examples/custom_type_derives.rs a little

* cargo fmt

* silcnce clippy in example

test-runtime/build.rs

@@ -98,7 +98,7 @@ async fn run() {
         r#"
         #[subxt::subxt(
             runtime_metadata_path = "{}",
-            generated_type_derives = "Debug, Eq, PartialEq"
+            generated_type_derives = "Eq, PartialEq"
         )]
         pub mod node_runtime {{
             #[subxt(substitute_type = "sp_arithmetic::per_things::Perbill")]