feat: Transformer middleware with DsProxy impl

[roynalnaruto]

Motivation

This PR adds support for proxy wallets, eg. DsProxy

Solution

• The Transformer trait must be implemented by a wallet like DsProxy
• The TransformerMiddleware can intercept and transform tx requests to send them as the appropriate txs that the proxy contract can execute.

Usage

• Using DsProxy as a Transformer

// instantiate wallet and provider
// instantiate signer middleware
let middleware = SignerMiddleware::new(provider, wallet);
let middleware = Arc::new(middleware);

// instantiate DsProxy as the transformer
let ds_proxy = DsProxy::build::<HttpWallet, Arc<HttpWallet>>(
    Arc::clone(&middleware),
    Some(ds_proxy_factory.address()),
    provider.address(),
).await?;
let transformer_middleware = TransformerMiddleware::new(Arc::clone(&middleware), ds_proxy);

// send txs via DsProxy
transformer_middleware.send_transaction(tx_request, None).await?.await?;

• Using DsProxy standalone

// instantiate DsProxy as the transformer
let ds_proxy = DsProxy::build::<HttpWallet, Arc<HttpWallet>>(
    Arc::clone(&middleware),
    Some(ds_proxy_factory.address()),
    provider.address(),
).await?;

// execute(bytes memory _code, bytes memory _data)
ds_proxy
    .execute::<HttpWallet, Arc<HttpWallet>>(
        Arc::clone(&middleware),
        AddressOrBytes::Bytes(bytecode),
        calldata,
    )
    .await;

// execute(address _target, bytes memory _data)
ds_proxy
    .execute::<HttpWallet, Arc<HttpWallet>>(
        Arc::clone(&middleware),
        AddressOrBytes::Address(target),
        calldata,
    )
    .await;

[gakonst]

So far so good! Left some comments. Thank you for the contribution as usual