Compact binary serde for TrieUpdates

[shekhirin]

Problem

We serialize TrieUpdates and StorageTrieUpdates using hex encoding for nibbles. It's fine for a human-readable format like JSON, but suboptimal for a binary one like bincode.

reth/crates/trie/trie/src/updates.rs

Lines 11 to 14 in b29d81c

	#[cfg_attr(feature = "serde", serde(serialize_with = "serialize_nibbles_map"))]
	pub(crate) account_nodes: HashMap<Nibbles, BranchNodeCompact>,
	#[cfg_attr(feature = "serde", serde(serialize_with = "serialize_nibbles_set"))]
	pub(crate) removed_nodes: HashSet<Nibbles>,

reth/crates/trie/trie/src/updates.rs

Lines 119 to 124 in b29d81c

	/// Collection of updated storage trie nodes.
	#[cfg_attr(feature = "serde", serde(serialize_with = "serialize_nibbles_map"))]
	pub(crate) storage_nodes: HashMap<Nibbles, BranchNodeCompact>,
	/// Collection of removed storage trie nodes.
	#[cfg_attr(feature = "serde", serde(serialize_with = "serialize_nibbles_set"))]
	pub(crate) removed_nodes: HashSet<Nibbles>,

Solution

Provide a custom serde implementation for these structs via serde_as, similar to #11331.