Improve `PayloadBuilderService` polling service

[tcoratger]

Describe the feature

At the moment, a new_job boolean flag is used and modified inside a while condition that drains all requests:

reth/crates/payload/builder/src/service.rs

Lines 232 to 274 in 82fb0ee

	// TODO(mattsse): this could be optmized so we only poll new jobs
	let mut new_job = false;
	// drain all requests
	while let Poll::Ready(Some(cmd)) = this.command_rx.poll_next_unpin(cx) {
	match cmd {
	PayloadServiceCommand::BuildNewPayload(attr, tx) => {
	let id = attr.payload_id();
	let mut res = Ok(id);
	if this.contains_payload(id) {
	warn!(%id, parent = ?attr.parent, "Payload job already in progress, ignoring.");
	} else {
	// no job for this payload yet, create one
	match this.generator.new_payload_job(attr) {
	Ok(job) => {
	this.metrics.inc_initiated_jobs();
	new_job = true;
	this.payload_jobs.push((job, id));
	}
	Err(err) => {
	this.metrics.inc_failed_jobs();
	warn!(?err, %id, "Failed to create payload builder job");
	res = Err(err);
	}
	}
	}
	// return the id of the payload
	let _ = tx.send(res);
	}
	PayloadServiceCommand::BestPayload(id, tx) => {
	let _ = tx.send(this.best_payload(id));
	}
	PayloadServiceCommand::Resolve(id, tx) => {
	let _ = tx.send(this.resolve(id));
	}
	}
	}
	if !new_job {
	return Poll::Pending
	}

At the end, if new_job is false, Poll::Pending is returned. We could improve the efficiency here by polling only new jobs.

Additional context

No response

[mattsse]

could be converted to futures unordered

[chirag-bgh]

I would like to take this.

[mattsse]

any update?
should I unassign you?

[chirag-bgh]

any update? should I unassign you?

Hey, yes I still want to work on this.
Just to confirm, we need to convert payload_jobs to FuturesUnordered right?