Figure out how to extract `IggyError` into an dedicated crate.

[numinnex]

#2519 prompted us with a good idea, we can use our rust error as a base for code generators in other SDKs to generate error status codes.
The tricky bit is to figure out project structure that would allow us to decouple the IggyError from server crate and put it into an dedicated crate, that can be versioned independently.

[hubcio]

This can be extended to binary interface of iggy protocol. We'd need to use some sort of IDL.

[hubcio]

I think we could use flatbuffers.

https://flatbuffers.dev/languages/rust/
https://github.com/frol/flatc-rust

  struct MessageHeader {
    checksum: uint64;
    id_low: uint64;
    id_high: uint64;
    offset: uint64;
    timestamp: uint64;
    origin_timestamp: uint64;
    user_headers_length: uint32;
    payload_length: uint32;
  }

For errors it would be harder because we have tons of sum types like Identifier, but still doable.