feat!: contract interfaces and better function calls

[Thunkar]

Closes #5081

This PR introduces autogenerated contract interfaces for easy intra and inter contract interactions. The aztec-macro crate is used to stub every non-internal private and public function and inject them into a ghost struct which has the same name as the contract that generated them. After that, they can be called like this:

contract ImportTest {

  use dep::my_imported_contract::MyImportedContract;

  #[aztec(private)]
  fn a_private_fn() {
    let deserialized_return = MyImportedContract::at(some_address).another_private_fn(arg1, arg2).call(&mut context);
    MyImportedContract::at(some_address).a_public_fn(arg1).enqueue(&mut context);
  }

  #[aztec(public)]
  fn a_public_fn() {
    let deserialized_return = MyImportedContract::at(some_address).a_public_fn(arg1).call(&mut context);
  }

  #[aztec(private)]
  fn calling_my_own_fns() {
    ImportTest::at(context.this_address).a_private_fn().call(&mut context);
    ImportTest::at(context.this_address).a_public_fn().enqueue(&mut context);
  }
  
}

Return values are deserialized_into() automatically, providing "real" return values thanks to #5633

Also, some general cleanup was required to allow importing contracts in another contracts. Main changes:

• HirContext.fully_qualified_struct_path now uses BFS to avoid returning the longest path when looking for a struct in a crate. This is required to avoid pulling structs usually imported in top-level dependencies (usually notes from our main contract) from other imported contracts.
• pack_args_oracle now has a slice mode in addition to its usual array mode.

PENDING:

AvmContext. The AVM team is discussing supporting args as slices. In case it's decided not to do that, a workaround could possibly be implemented using the macro, but it would be fairly complex.

Thanks to @fcarreiro and the amazing AVM team, this is now supported for the AvmContext!