Compare different `sort` variants for LDK's `get_route`.

sort_compare.rs

	let mut paths_cached = payment_paths.clone();
	let instant_cached = Instant::now();
	paths_cached.sort_by_cached_key(|path| path.get_total_fee_paid_msat());
	println!("Cached sort took: {}", instant_cached.elapsed().as_nanos());

	let mut paths_unstable = payment_paths.clone();
	let instant_unstable = Instant::now();
	paths_unstable.sort_unstable_by_key(|path| path.get_total_fee_paid_msat());
	println!("Unstable sort took: {}", instant_unstable.elapsed().as_nanos());

	let mut paths_stable = payment_paths.clone();
	let instant_stable = Instant::now();
	paths_stable.sort_by_key(|path| path.get_total_fee_paid_msat());
	println!("Stable sort took: {}", instant_stable.elapsed().as_nanos());