perf: replace BytesMut with alloy_rlp::encode

[estensen]

Ref #6986

Some issues running the tests locally

cargo test --workspace
...
     Running unittests src/lib.rs (target/debug/deps/reth_etl-9ce46664de48f371)

running 1 test
test tests::etl_hashes ... FAILED

failures:

---- tests::etl_hashes stdout ----
thread 'tests::etl_hashes' panicked at crates/etl/src/lib.rs:280:36:
called `Result::unwrap()` on an `Err` value: Custom { kind: Uncategorized, error: PathError { path: "/var/folders/qd/736ntn5d55d5l1c23gvwtgm40000gn/T/.tmpOTLFBA/.tmpBM6ObO", err: Os { code: 24, kind: Uncategorized, message: "Too many open files" } } }
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace


failures:
    tests::etl_hashes

test result: FAILED. 0 passed; 1 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.03s

Or is it sufficient to run cargo test (which passes) here? Pretty new with Rust.

[DaniPopes]

You can target specific crates with -p package or reduce the number of threads executing with -j n, I would defer to CI anyway for running all tests

[DaniPopes]

I've removed 'fixes' because there are still calls, I would like for all of them to be removed.