EAD labels > 23 are misencoded, discarding criticality

[chrysn]

I think that the only label/criticality combinations that are currently encoded right are ([1..23], false).

While the decoder properly distinguishes between u8 and i8 values, and can at least decode the simple ones right. However, encoding 25 results in a parser error later.

[edit:] Adding some context: Imlpementing draft-ietf-ace-edhoc-oscore-profile-06, I have to use some value for the "ACE-OAuth Access Token" item. As no early allocation is happening yet, I'll have to make a guess, and I'd have guessed 25. I guess I'll update my guess to 20.

CC'ing @malishav who is DE for that registry and may want to earmark something.