feat(ethexe): add an attribute `#[sails_rs::return(...)]` to specify name of returned values from function

[StackOverflowExcept1on]

Problem to Solve

#[sails_rs::service(events = Events)]
impl SomeService {
    #[sails_rs::return(r1)]
    pub async fn do_this(&mut self, p1: u32, p2: sails_rs::String) -> u32 {
        self.emit_eth_event(Events::DoThisEvent(p1 * 2, p2 + "hey from sails!")).unwrap();
        p1 * 2
    }
    #[sails_rs::return(r1)]
    pub fn this(&self, p1: bool) -> bool {
        !p1
    }
}

We can then use this name when generating callbacks:

// SPDX-License-Identifier: UNLICENSED
pragma solidity ^0.8.28;

interface IEthAppWithEventsCallbacks {
    function replyOn_svc1DoThis(bytes32 messageId, uint32 r1) external;

    function replyOn_svc1This(bytes32 messageId, bool r1) external;

    function errorReply(bytes32 messageId, bytes4 replyCode) external;
}

This should also work for tuples. The user can add multiple #[sails_rs::return(r1)] on each line, similar to Solidity's docstrings: https://github.com/StackOverflowExcept1on/frost-secp256k1-evm/blob/40ad4da33913be370ba304be3918dee64430ad09/src/FROST.sol#L68-L69

Possible Solution

N/A

Notes

No response