#2650 switch contact.individual_prefix tokens to contact.prefix_id:label

The token processor code was updated to handle the label syntax in
https://github.com/civicrm/civicrm-core/pull/21570 with tests added.
The greeting processing still doesn't go through the token processor.
I'm trying to fix that but that change has a few moving parts so
chasing out our last reference to contact.prefix_id in this PR
and also doing the DB updates to switch over to use the preferred
tokens and make them work with
replaceGreetingTokens (albeit hopefully in the
short-ish term we will stop using that function)