add NodeFeatures field to HostConfiguration and runtime API (#2177)

Adds a `NodeFeatures` bitfield value to the runtime `HostConfiguration`,
with the purpose of coordinating the enabling of node-side features,
such as: https://github.com/paritytech/polkadot-sdk/issues/628 and
https://github.com/paritytech/polkadot-sdk/issues/598.
These are features that require all validators enable them at the same
time, assuming all/most nodes have upgraded their node versions.

This PR doesn't add any feature yet. These are coming in future PRs.

Also adds a runtime API for querying the state of the client features
and an extrinsic for setting/unsetting a feature by its index in the bitfield.

Note: originally part of:
https://github.com/paritytech/polkadot-sdk/pull/1644, but posted as
standalone to be reused by other PRs until the initial PR is merged

cumulus/client/relay-chain-rpc-interface/src/rpc_client.rs

@@ -31,7 +31,9 @@ use parity_scale_codec::{Decode, Encode};
 use cumulus_primitives_core::{
 	relay_chain::{
 		async_backing::{AsyncBackingParams, BackingState},
-		slashing, BlockNumber, CandidateCommitments, CandidateEvent, CandidateHash,
+		slashing,
+		vstaging::NodeFeatures,
+		BlockNumber, CandidateCommitments, CandidateEvent, CandidateHash,
 		CommittedCandidateReceipt, CoreState, DisputeState, ExecutorParams, GroupRotationInfo,
 		Hash as RelayHash, Header as RelayHeader, InboundHrmpMessage, OccupiedCoreAssumption,
 		PvfCheckStatement, ScrapedOnChainVotes, SessionIndex, SessionInfo, ValidationCode,
@@ -597,6 +599,14 @@ impl RelayChainRpcClient {
 			.await
 	}
 
+	pub async fn parachain_host_node_features(
+		&self,
+		at: RelayHash,
+	) -> Result<NodeFeatures, RelayChainError> {
+		self.call_remote_runtime_function("ParachainHost_node_features", at, None::<()>)
+			.await
+	}
+
 	pub async fn parachain_host_disabled_validators(
 		&self,
 		at: RelayHash,