Add constants for "Nil UUID", "Max UUID" (from draft "new UUID" spec) in `UUIDUtil`

[cowtowncoder]

(note: related to Draft-04 spec at: https://uuid6.github.io/uuid6-ietf-draft/ section 5.4)

So, looks like there will be the counterpart for "null UUID" (all zeroes) wherein all 128 bits are 1s, so-called "Max UUID".
This is specific in section 5.4 of the "new UUID" draft spec (draft-04):

https://www.ietf.org/archive/id/draft-peabody-dispatch-new-uuid-format-04.html

It should probably be defined similar to the existing null UUID (details to be filled)