Stop using singleton instance on Dart bindings

[erdemyerebasmaz]

This PR implements frb v2 Methods support.

• connect now returns a BindingsBreezServices which we can call BreezServices API from.

TODO:

• [ ] Add migration guide.
• [ ] See if it's possible to get rid of BreezSDK wrapper class as a whole, or slim it down as much as possible
  • For example, checking if Dart streams can be managed on Rust side via Rust call Dart or
  • Generating event listener logic via: Extra Dart code

[erdemyerebasmaz]

I think it's looking good

Thanks. I'm thinking of writing the migration guide and merging the changes.

I'll open an issue for

See if it's possible to get rid of BreezSDK wrapper class as a whole, or slim it down as much as possible

• For example, checking if Dart streams can be managed on Rust side via Rust call Dart or
• Generating event listener logic via: Extra Dart code

and address it in scope of another PR.