Constant MAX_KBUCKET_INDEX

pub const MAX_KBUCKET_INDEX: usize = 255;

Max kbucket index is 255.

This is the max log2distance for 32 byte NodeId - 1. See https://github.com/sigp/discv5/blob/e9e0d4f93ec35591832a9a8d937b4161127da87b/src/kbucket.rs#L586-L587.