add MethodError implementation for SolError derive macro

[qalisander]

Description

Adds implementation of stylus_sdk::call::MethodError trait inside SolidityError macro.
MethodError trait is necessary for error types inside SolidityError enum.
By the end it will be possible to nest error like this:

#[derive(SolidityError, Debug)]
pub enum Error {
    Erc721(erc721::Error),
    Checkpoint(checkpoints::Error),
    ForbiddenBatchMint(ERC721ForbiddenBatchMint),
    ExceededMaxBatchMint(ERC721ExceededMaxBatchMint),
    ForbiddenMint(ERC721ForbiddenMint),
    ForbiddenBatchBurn(ERC721ForbiddenBatchBurn),
}

Resolves #135

Checklist

• I have documented these changes where necessary.
• I have read the DCO and ensured that these changes comply.
• I assign this work under its open source licensing.