fix(discv5): flip exact bit in node id

[emhane]

Describe the feature

Rn FINDNODE target selection in discv5, flips a whole byte. Actually it should flip only the specific bit at the given kbucket_index in the local node id. The bits[kbucket_index + 1..] should all be random.

reth/crates/net/discv5/src/lib.rs

Lines 535 to 556 in d599ce4

	/// Gets the next lookup target, based on which bucket is currently being targeted.
	pub fn get_lookup_target(
	kbucket_index: usize,
	local_node_id: discv5::enr::NodeId,
	) -> discv5::enr::NodeId {
	// init target
	let mut target = local_node_id.raw();
	// make sure target has a 'log2distance'-long suffix that differs from local node id
	if kbucket_index != 0 {
	let suffix_bit_offset = MAX_KBUCKET_INDEX.saturating_sub(kbucket_index);
	let suffix_byte_offset = suffix_bit_offset / 8;
	// todo: flip the precise bit
	// let rel_suffix_bit_offset = suffix_bit_offset % 8;
	target[suffix_byte_offset] = !target[suffix_byte_offset];
	if suffix_byte_offset != 31 {
	for b in target.iter_mut().take(31).skip(suffix_byte_offset + 1) {
	*b = rand::random::<u8>();
	}
	}
	}

Additional context

No response