getters should return references to types that are not Copy

[tdelabro]

macro_rules! implement_deploy_account_tx_getters {
    ($(($field:ident, $field_type:ty)),*) => {
        $(
            pub fn $field(&self) -> $field_type {
                match self {
                    Self::V1(tx) => tx.$field.clone(),
                    Self::V3(tx) => tx.$field.clone(),
                }
            }
        )*
    };
}

...

impl DeployAccountTransaction {
    implement_deploy_account_tx_getters!(
        (class_hash, ClassHash),
        (constructor_calldata, Calldata),
        (contract_address_salt, ContractAddressSalt),
        (nonce, Nonce),
        (signature, TransactionSignature)
    );

Calling clone is not a problem for types that implement copy, but for types that don't. Like TransactionSignature, it means that a clone operation always occurs, even when the caller has no need for ownership of the value and could have used a reference.
This has a performance cost and is overall a bad design for an API: the method should not assume anything about the caller intentions