PoV Reclaim (Clawback) Node Side (#1462)

This PR provides the infrastructure for the pov-reclaim mechanism
discussed in #209. The goal is to provide the current proof size to the
runtime so it can be used to reclaim storage weight.

## New Host Function
- A new host function is provided
[here](https://github.com/skunert/polkadot-sdk/blob/5b317fda3be205f4136f10d4490387ccd4f9765d/cumulus/primitives/pov-reclaim/src/lib.rs#L23).
It returns the size of the current proof size to the runtime. If
recording is not enabled, it returns 0.

## Implementation Overview
- Implement option to enable proof recording during import in the
client. This is currently enabled for `polkadot-parachain`,
`parachain-template` and the cumulus test node.
- Make the proof recorder ready for no-std. It was previously only
enabled for std environments, but we need to record the proof size in
`validate_block` too.
- Provide a recorder implementation that only the records the size of
incoming nodes and does not store the nodes itself.
- Fix benchmarks that were broken by async backing changes
- Provide new externalities extension that is registered by default if
proof recording is enabled.
- I think we should discuss the naming, pov-reclaim was more intuitive
to me, but we could also go with clawback like in the issue.

## Impact of proof recording during import
With proof recording: 6.3058 Kelem/s
Without proof recording: 6.3427 Kelem/s

The measured impact on the importing performance is quite low on my
machine using the block import benchmark. With proof recording I am
seeing a performance hit of 0.585%.

---------

Co-authored-by: command-bot <>
Co-authored-by: Davide Galassi <davxy@datawok.net>
Co-authored-by: Bastian Köcher <git@kchr.de>

substrate/primitives/trie/src/lib.rs

@@ -30,6 +30,9 @@ mod storage_proof;
 mod trie_codec;
 mod trie_stream;
 
+#[cfg(feature = "std")]
+pub mod proof_size_extension;
+
 /// Our `NodeCodec`-specific error.
 pub use error::Error;
 /// Various re-exports from the `hash-db` crate.
@@ -146,6 +149,29 @@ where
 	}
 }
 
+/// Type that is able to provide a [`trie_db::TrieRecorder`].
+///
+/// Types implementing this trait can be used to maintain recorded state
+/// across operations on different [`trie_db::TrieDB`] instances.
+pub trait TrieRecorderProvider<H: Hasher> {
+	/// Recorder type that is going to be returned by implementors of this trait.
+	type Recorder<'a>: trie_db::TrieRecorder<H::Out> + 'a
+	where
+		Self: 'a;
+
+	/// Create a [`StorageProof`] derived from the internal state.
+	fn drain_storage_proof(self) -> Option<StorageProof>;
+
+	/// Provide a recorder implementing [`trie_db::TrieRecorder`].
+	fn as_trie_recorder(&self, storage_root: H::Out) -> Self::Recorder<'_>;
+}
+
+/// Type that is able to provide a proof size estimation.
+pub trait ProofSizeProvider {
+	/// Returns the storage proof size.
+	fn estimate_encoded_size(&self) -> usize;
+}
+
 /// TrieDB error over `TrieConfiguration` trait.
 pub type TrieError<L> = trie_db::TrieError<TrieHash<L>, CError<L>>;
 /// Reexport from `hash_db`, with genericity set for `Hasher` trait.