feat: suggest gas price based on latest block's transactions

[yiweichi]

This PR focus on implementing a simplified version of the GPO without needing to look at the tx pool, however look at the status of latest block. Suggest gas price base on if the latest block is at capacity. this will help to:

• reduce node configuration complexity by removing congestion threshold parameter
• reduce RPC node overhead by removing expensive query of tx pool size
• enable private mempool while any RPC node is still able to provide reasonable gas price estimate

Two JSON_RPC methods are effected.

1. eth_gasPrice, if the latest block is not at capacity, this will return a minimal suggest gas price.
2. eth_feeHistory, if the latest block is not at capacity, the reward field of return will be the minimal suggest gas price.

[codspeed-hq]

CodSpeed Performance Report

Merging #291 will not alter performance

_{Comparing feat-simplify-gas-price-oracle (50e096e) with scroll (357655f)}

Summary

✅ 77 untouched benchmarks

[frisitano]

I will leave review of the logic to @jonastheis and @greged93 who have better gas oracle related context. However, I wonder if we can avoid making changes to crates/rpc/rpc-eth-types/src/gas_oracle.rs and instead exclusively use overrides in crates/scroll/* code? Our objective is to minimise our fork diff with upstream.

[yiweichi]

I will leave review of the logic to @jonastheis and @greged93 who have better gas oracle related context. However, I wonder if we can avoid making changes to crates/rpc/rpc-eth-types/src/gas_oracle.rs and instead exclusively use overrides in crates/scroll/* code? Our objective is to minimise our fork diff with upstream.

Yes, that's a good one. I tried to keep crates/rpc/rpc-eth-types/src/gas_oracle.rs as is or make as less changes as possible, but can't find a good way to do so. Mainly because GasPriceOracle on Reth is a struct instead of a trait, seems hard to override it on crates/scroll/*.
@greged93 may I ask any input on this?

[greged93]

couple of comments but looks good!

[greged93]

@greged93 may I ask any input on this?

It looks a little tricky yes, upstream would need to abstract the GasOracle, right now I don't really see any solution.

[greged93]

noticed some default values that I think need to be updated.

[greged93]

Couple of small comments and questions, I think we can merge after this!

[greged93]

lgtm!