enhancement(derives): extend enum macro to accept any ident and refactor enums

[borngraced]

#1595
Previously, the EnumFromStringy macro was exclusively utilized to produce the From trait from one enum to another enum only when the inner identifier was "String". However, to enhance this utility, I've expanded the macro's functionality to allow any identifier.

This will eliminates the need for code repetition such as the following while decreasing the codebase to some extent :) :

impl From<rlp::DecoderError> for ValidatePaymentError {
    fn from(err: rlp::DecoderError) -> Self { Self::TxDeserializationError(err.to_string()) }
}

impl From<web3::Error> for ValidatePaymentError {
    fn from(err: web3::Error) -> Self { Self::Transport(err.to_string()) }
}

impl From<NumConversError> for ValidatePaymentError {
    fn from(err: NumConversError) -> Self { Self::InternalError(err.to_string()) }
}

impl From<SPVError> for ValidatePaymentError {
    fn from(err: SPVError) -> Self { Self::SPVError(err) }
}

impl From<serialization::Error> for ValidatePaymentError {
    fn from(err: serialization::Error) -> Self { Self::TxDeserializationError(err.to_string()) }
}

impl From<UnexpectedDerivationMethod> for ValidatePaymentError {
    fn from(err: UnexpectedDerivationMethod) -> Self { Self::InternalError(err.to_string()) }
}


And just do this instead 


pub enum ValidatePaymentError {
    /// Should be used to indicate internal MM2 state problems (e.g., DB errors, etc.).
    #[from_stringify("NumConversError", "UnexpectedDerivationMethod", "keys::Error")]
    InternalError(String),
    /// Problem with deserializing the transaction, or one of the transaction parts is invalid.
    #[from_stringify("rlp::DecoderError", "serialization::Error")]
    TxDeserializationError(String),
    /// SPV client error.
    #[from_stringify("SPVError")]
    SPVError(SPVError),
    …
}


So it doesn’t matter if a field inner ident is string or not

[dimxy]

btw there is a similar feature https://docs.rs/thiserror/latest/thiserror/. An interesting feature in it is formatting error message with interpolating nested error

[borngraced]

btw there is a similar feature https://docs.rs/thiserror/latest/thiserror/. An interesting feature in it is formatting error message with interpolating nested error

seems cool really, but it still depends on anyhow error crate. we might want to keep this and keep extending I guess

[shamardy]

@borngraced please resolve conflicts in this PR.