pvf-precheck: PVF pre-checker subsystem (#4643)

This commit implements the last major piece of #3211: the subsystem that
tracks PVFs that require voting, issues pre-check requests to
candidate-validation and makes sure that the votes are submitted to the
chain.

polkadot/node/overseer/src/lib.rs

@@ -84,8 +84,8 @@ use polkadot_node_subsystem_types::messages::{
 	BitfieldSigningMessage, CandidateBackingMessage, CandidateValidationMessage, ChainApiMessage,
 	ChainSelectionMessage, CollationGenerationMessage, CollatorProtocolMessage,
 	DisputeCoordinatorMessage, DisputeDistributionMessage, GossipSupportMessage,
-	NetworkBridgeEvent, NetworkBridgeMessage, ProvisionerMessage, RuntimeApiMessage,
-	StatementDistributionMessage,
+	NetworkBridgeEvent, NetworkBridgeMessage, ProvisionerMessage, PvfCheckerMessage,
+	RuntimeApiMessage, StatementDistributionMessage,
 };
 pub use polkadot_node_subsystem_types::{
 	errors::{SubsystemError, SubsystemResult},
@@ -420,6 +420,9 @@ pub struct Overseer<SupportsParachains> {
 	#[subsystem(no_dispatch, CandidateValidationMessage)]
 	candidate_validation: CandidateValidation,
 
+	#[subsystem(no_dispatch, PvfCheckerMessage)]
+	pvf_checker: PvfChecker,
+
 	#[subsystem(no_dispatch, CandidateBackingMessage)]
 	candidate_backing: CandidateBacking,