Add tests and modify as_vec implementation (#3715)

* Add tests and modify as_vec implementation

* Address feedback

* fix typo in test

polkadot/node/network/availability-recovery/src/lib.rs

@@ -363,11 +363,9 @@ impl RequestChunksPhase {
 
 					let validator_index = chunk.index;
 
-					if let Ok(anticipated_hash) = branch_hash(
-						&params.erasure_root,
-						&chunk.proof_as_vec(),
-						chunk.index.0 as usize,
-					) {
+					if let Ok(anticipated_hash) =
+						branch_hash(&params.erasure_root, chunk.proof(), chunk.index.0 as usize)
+					{
 						let erasure_chunk_hash = BlakeTwo256::hash(&chunk.chunk);
 
 						if erasure_chunk_hash != anticipated_hash {