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>

cumulus/test/service/src/main.rs

@@ -128,7 +128,7 @@ fn main() -> Result<(), sc_cli::Error> {
 				})
 				.unwrap_or(cumulus_test_service::Consensus::RelayChain);
 
-			let (mut task_manager, _, _, _, _) = tokio_runtime
+			let (mut task_manager, _, _, _, _, _) = tokio_runtime
 				.block_on(cumulus_test_service::start_node_impl(
 					config,
 					collator_key,
@@ -139,6 +139,7 @@ fn main() -> Result<(), sc_cli::Error> {
 					|_| Ok(jsonrpsee::RpcModule::new(())),
 					consensus,
 					collator_options,
+					true,
 				))
 				.expect("could not create Cumulus test service");