[Providers] Use `EthApi` for embedded rollup node

[frisitano]

Overview

We are sensitive to the latency of the RPC when fetching blocks and executing requests against the EN from the rollup node. Currently, we are using the http provider from the EN. Instead, we should migrate to using the EthApi, which is an in-process type that can serve all eth_ related requests. This should have much lower latency and improve performance. We should also maintain support for a network-based RPC, possibly by implementing alloy_provider::Provider<Scroll> on the EthApi, but this idea should be analyzed and validated. Below is an example of how we fetch the EthApi from the node.

rollup-node/crates/node/tests/e2e.rs

Line 960 in f3674d8

let rpc = node.rpc.inner.eth_api();