clearId

Used to construct a globally unique channel ID.
The full globally unique ID will be: "name.id" where ID is shown as base36.
Assuming that the number of meshtastic users is below 20K (true for a long time)
the chance of this 64 bit random number colliding with anyone else is super low.
And the penalty for collision is low as well, it just means that anyone trying to decrypt channel messages might need to
try multiple candidate channels.
Any time a non wire compatible change is made to a channel, this field should be regenerated.
There are a small number of 'special' globally known (and fairly) insecure standard channels.
Those channels do not have a numeric id included in the settings, but instead it is pulled from
a table of well known IDs.
(see Well Known Channels FIXME)