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/primitives/proof-size-hostfunction/Cargo.toml

@@ -0,0 +1,21 @@
+[package]
+name = "cumulus-primitives-proof-size-hostfunction"
+version = "0.1.0"
+authors.workspace = true
+edition.workspace = true
+description = "Hostfunction exposing storage proof size to the runtime."
+license = "Apache-2.0"
+
+[dependencies]
+sp-runtime-interface = { path = "../../../substrate/primitives/runtime-interface", default-features = false }
+sp-externalities = { path = "../../../substrate/primitives/externalities", default-features = false }
+sp-trie = { path = "../../../substrate/primitives/trie", default-features = false }
+
+[dev-dependencies]
+sp-state-machine = { path = "../../../substrate/primitives/state-machine" }
+sp-core = { path = "../../../substrate/primitives/core" }
+sp-io = { path = "../../../substrate/primitives/io" }
+
+[features]
+default = [ "std" ]
+std = [ "sp-externalities/std", "sp-runtime-interface/std", "sp-trie/std" ]