Decouple Nautilus' IDL crate from the main crate

[buffalojoec]

Solana Labs and ecosystem members have long been discussing an "IDL Standard" - which would basically impose an interface for all IDLs to adhere to, but allow them to implement their own additional configurations.

https://forum.solana.com/t/srfc-00008-idl-standard/66/8

Nautilus currently uses it's own IDL crate, which was by design so that it could leverage additional configs.

We should:

• Fork the IDL crate from one of the following repositories:
  • https://github.com/metaplex-foundation/shank/tree/master/shank-idl
  • https://github.com/ironforge-cloud/solana-idl
  • https://github.com/solana-idl-foundation/solana-idl-spec
• Modify that crate so that it establishes an IDL interface with extendible configurations
  • This can be done with generics such as Option<T>
  • As long as the main IDL created using this crate adheres to the interface

The idea here is to introduce a crate - for everyone across Solana to use - that allows you to create your own custom IDL that adheres to the interface.
Nautilus would then just use this crate within its source like any other project would.