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/runtime-interface/proc-macro/Cargo.toml

@@ -20,4 +20,5 @@ Inflector = "0.11.4"
 proc-macro-crate = "1.1.3"
 proc-macro2 = "1.0.56"
 quote = "1.0.28"
+expander = "2.0.0"
 syn = { version = "2.0.38", features = ["full", "visit", "fold", "extra-traits"] }

substrate/primitives/runtime-interface/proc-macro/src/runtime_interface/mod.rs

@@ -68,5 +68,11 @@ pub fn runtime_interface_impl(
 		}
 	};
 
+	let res = expander::Expander::new("runtime_interface")
+		.dry(std::env::var("EXPAND_MACROS").is_err())
+		.verbose(true)
+		.write_to_out_dir(res)
+		.expect("Does not fail because of IO in OUT_DIR; qed");
+
 	Ok(res)
 }