feature: add possibility to reuse error for the other contract

[qalisander]

It is convenient to declare errors in different modules. And reuse the error from the other module inside an enum.

Currently the following pattern for error structure doesn't work for SolidityError proc macro:

#[derive(SolidityError, Debug)]
pub enum Error {
    Erc721(Erc721Error),
    Checkpoints(CheckpointError),
    ForbiddenBatchMint(ERC721ForbiddenBatchMint),
    ExceededMaxBatchMint(ERC721ExceededMaxBatchMint),
    ForbiddenMint(ERC721ForbiddenMint),
    ForbiddenBatchBurn(ERC721ForbiddenBatchBurn),
}

#[derive(SolidityError, Debug)]
pub enum Erc721Error {
    InsufficientBalance(ERC721InsufficientBalance),
    InvalidSender(ERC721InvalidSender),
    InvalidReceiver(ERC721InvalidReceiver),
    InsufficientAllowance(ERC721InsufficientAllowance),
    InvalidSpender(ERC721InvalidSpender),
}

#[derive(SolidityError, Debug)]
pub enum CheckpointError {
    CheckpointUnorderedInsertion(CheckpointUnorderedInsertion),
}

Compilation fails with: "the trait bound Error: stylus_sdk::call::MethodError is not satisfied".

[0xNeshi]

We would also need the inherited error enums to implement the SolError trait for devs to be able to export ABI of contracts that use the pattern described in this issue (for a more detailed explanation see OpenZeppelin/rust-contracts-stylus#439 (comment)).