Plumbing to increase pvf workers configuration based on chain id (#4252)

Part of https://github.com/paritytech/polkadot-sdk/issues/4126 we want
to safely increase the execute_workers_max_num gradually from chain to
chain and assess if there are any negative impacts.

This PR performs the necessary plumbing to be able to increase it based
on the chain id, it increase the number of execution workers from 2 to 4
on test network but lives kusama and polkadot unchanged until we gather
more data.

---------

Signed-off-by: Alexandru Gheorghe <alexandru.gheorghe@parity.io>

polkadot/node/core/candidate-validation/src/lib.rs

@@ -100,6 +100,13 @@ pub struct Config {
 	pub prep_worker_path: PathBuf,
 	/// Path to the execution worker binary
 	pub exec_worker_path: PathBuf,
+	/// The maximum number of pvf execution workers.
+	pub pvf_execute_workers_max_num: usize,
+	/// The maximum number of pvf workers that can be spawned in the pvf prepare pool for tasks
+	/// with the priority below critical.
+	pub pvf_prepare_workers_soft_max_num: usize,
+	/// The absolute number of pvf workers that can be spawned in the pvf prepare pool.
+	pub pvf_prepare_workers_hard_max_num: usize,
 }
 
 /// The candidate validation subsystem.
@@ -224,6 +231,9 @@ async fn run<Context>(
 		secure_validator_mode,
 		prep_worker_path,
 		exec_worker_path,
+		pvf_execute_workers_max_num,
+		pvf_prepare_workers_soft_max_num,
+		pvf_prepare_workers_hard_max_num,
 	}: Config,
 ) -> SubsystemResult<()> {
 	let (validation_host, task) = polkadot_node_core_pvf::start(
@@ -233,6 +243,9 @@ async fn run<Context>(
 			secure_validator_mode,
 			prep_worker_path,
 			exec_worker_path,
+			pvf_execute_workers_max_num,
+			pvf_prepare_workers_soft_max_num,
+			pvf_prepare_workers_hard_max_num,
 		),
 		pvf_metrics,
 	)