Allow alloy to estimate tx gas

[0xOmarA]

Summary

This PR allows for the gas to be estimated using alloy, which fixes some of the earlier issues we were seeing in the contract deployment.

Description

I was seeing some errors in the deployment of contracts and more specifically the following two errors:

  2025-07-12T18:33:54.129855Z ERROR revive_dt_core::driver: Failed to execute transaction when deploying the contract on node : "revive_dt_core::Geth", "Callable", server returned an error response: error code -32000: gas uint64 overflow

2025-07-12 19:13:38.836 DEBUG tokio-runtime-worker runtime::revive: try_into_checked_extrinsic: gas_price: 5000000, encoded_len: 1944 actual_fee: 19441617794180 eth_fee: 25000000    
2025-07-12 19:13:38.836 DEBUG tokio-runtime-worker runtime::revive: eth fees 25000000 too low, actual fees: 19441617794180    
2025-07-12 19:13:38.840 ERROR tokio-runtime-worker sc_service::task_manager: Essential task `txpool-background` failed. Shutting down service.    

These two issues had different causes:

1. When constructing transactions we put the gas values ourselves and they were not representative of how much is needed to deploy the contracts.
2. We were using String::into_bytes to convert the hex-encoded contract code into bytes which utf-8 encodes the string instead of performing a hex-decode.

So, this PR does the following:

1. Correctly uses hex::decode to decode the contract hex-encoded byte code into a vector of bytes.
2. Allows for alloy to perform the gas estimation for us (by not providing the fields and letting it fill them in)

[xermicus]

Thanks