Improve `wallet_getAssets`

[joshieDo]

Right now wallet_getAssets will make a multicall request per asset, including metadata and balance.

relay/src/rpc/relay.rs

Lines 2745 to 2752 in 07fa527

	let (balance, decimals, name, symbol) = chain_provider
	.multicall()
	.add(erc20.balanceOf(request.account))
	.add(erc20.decimals())
	.add(erc20.name())
	.add(erc20.symbol())
	.aggregate()
	.await?;

However this could be greatly improved by batching assets into one/many multicalls just for balanceOf and then using the following to get each asset metadata:

relay/src/asset.rs

Lines 62 to 71 in 07fa527

	/// Lookup asset info for a given chain and a list of assets. It first checks the cache, and if
	/// it cannot find it will query it from chain.
	///
	/// # Note:
	/// Ensures that the returned map contains all the requested assets.
	pub async fn get_asset_info_list<P: Provider>(
	&self,
	provider: &P,
	assets: Vec<Asset>,
	) -> Result<HashMap<Asset, AssetWithInfo>, RelayError> {

[mablr]

I'd like to give a try 👍