Code, PoV compression and remove CompressedPoV struct (#2852)

* use compressed blob in candidate-validation

* add some tests for compressed code blobs

* remove CompressedPoV and apply compression in collation-generation

* decompress BlockData before executing

* don't produce oversized collations

* add test for PoV decompression failure

* fix tests and clean up

* fix test

* address review and fix CI

* take this )

polkadot/node/network/availability-distribution/src/responder.rs

@@ -16,11 +16,13 @@
 
 //! Answer requests for availability chunks.
 
+use std::sync::Arc;
+
 use futures::channel::oneshot;
 
 use polkadot_node_network_protocol::request_response::{request::IncomingRequest, v1};
 use polkadot_primitives::v1::{CandidateHash, ValidatorIndex};
-use polkadot_node_primitives::{AvailableData, CompressedPoV, ErasureChunk};
+use polkadot_node_primitives::{AvailableData, ErasureChunk};
 use polkadot_subsystem::{
 	messages::{AllMessages, AvailabilityStoreMessage},
 	SubsystemContext, jaeger,
@@ -100,18 +102,7 @@ where
 	let response = match av_data {
 		None => v1::PoVFetchingResponse::NoSuchPoV,
 		Some(av_data) => {
-			let pov = match CompressedPoV::compress(&av_data.pov) {
-				Ok(pov) => pov,
-				Err(error) => {
-					tracing::error!(
-						target: LOG_TARGET,
-						error = ?error,
-						"Failed to create `CompressedPov`",
-					);
-					// this should really not happen, let this request time out:
-					return Err(Error::PoVDecompression(error))
-				}
-			};
+			let pov = Arc::try_unwrap(av_data.pov).unwrap_or_else(|a| (&*a).clone());
 			v1::PoVFetchingResponse::PoV(pov)
 		}
 	};