feat: initial implementation of OpenRPC definitions for methods

[aatifsyed]

Summary of changes

• crate::rpc::reflect::SelfDescribingRpcModule creates OpenRPC definitions for methods
• chain_get_path uses that struct
• cleanup error types
• add TODOs for various issues

Follow up

#4032

Change checklist

• I have performed a self-review of my own code,
• I have made corresponding changes to the documentation,
• I have added tests that prove my fix is effective or that my feature works (if possible),
• I have made sure the CHANGELOG is up-to-date. All user-facing changes should be reflected in this document.

[LesnyRumcajs]

Let's have an issue with the context for this PR. What problem does it solve? Why is it needed? What decisions needed to be made?

[LesnyRumcajs]

1. In general, should the reflect code live in the Forest repository? Could it potentially live elsewhere and be published to crates.io as something others could reuse?
2. As noted elsewhere, panics are rough. Can they be avoided so that the error can be handled by the caller?

[aatifsyed]

1. In general, should the reflect code live in the Forest repository? Could it potentially live elsewhere and be published to crates.io as something others could reuse?
2. As noted elsewhere, panics are rough. Can they be avoided so that the error can be handled by the caller?

1. I think reflect could be broken out, but that can be a later PR - maybe once it's had more use. I'm also meh about jsonrpsee in general - I feel more restricted than enabled by it.
2. I think the existing panics are appropriate. They're not handle-able, they require code to be written to fix. I think it follows the same precedence as tokio::spawn or axum::Router::route.

[LesnyRumcajs]

Approving. That said, I have my doubts regarding the design decision of having panics here. I hope it won't bite us in the future.

[ruseinov]

This is looking good!

I have submitted some comments, mostly regarding docs.

This code is quite hard to read due to the specifics of the problem it's trying to solve, so it would be nice to make sure it's well-documented, so the next time it needs to be touched it wouldn't take as much brain space as it does to review it.

Especially the macros, parser and serde code.

Done