Further improved availability recovery (#3711)

* WiP.

* Things compile.

* cargo fmt

* Passing tests + fix warnings.

* Metrics for availability recovery.

* Basic test.

* Fix typos and actually check for overflow.

* cargo fmt

* Register metrics.

* More tests.

* Fix warning.

* cargo +nightly fmt

* Fix metrics

* Get rid of unsafe.

* tabify

* spellcheck

Co-authored-by: Andronik Ordian <write@reusable.software>
Co-authored-by: Bastian Köcher <info@kchr.de>

polkadot/node/network/protocol/src/request_response/mod.rs

@@ -89,6 +89,9 @@ const DEFAULT_REQUEST_TIMEOUT: Duration = Duration::from_secs(3);
 /// peer set as well).
 const DEFAULT_REQUEST_TIMEOUT_CONNECTED: Duration = Duration::from_secs(1);
 
+/// Timeout for requesting availability chunks.
+pub const CHUNK_REQUEST_TIMEOUT: Duration = DEFAULT_REQUEST_TIMEOUT_CONNECTED;
+
 /// This timeout is based on what seems sensible from a time budget perspective, considering 6
 /// second block time. This is going to be tough, if we have multiple forks and large PoVs, but we
 /// only have so much time.
@@ -132,7 +135,7 @@ impl Protocol {
 				max_request_size: 1_000,
 				max_response_size: POV_RESPONSE_SIZE as u64 / 10,
 				// We are connected to all validators:
-				request_timeout: DEFAULT_REQUEST_TIMEOUT_CONNECTED,
+				request_timeout: CHUNK_REQUEST_TIMEOUT,
 				inbound_queue: Some(tx),
 			},
 			Protocol::CollationFetching => RequestResponseConfig {