Changed the min OS version to iOS 13.0 (support for 'Identifiable')
Removed the alternate approaches to fetching the userKeyPair and userPublicKeyHexString (no consistently routed through the caching method)
Migrated the 'OWSIdentityManager' logic to use the new 'Identity' type
Added the 'Setting' table and got the pattern working fairly nicely (unfortunately there isn't a good way to avoid key collision without proper enums)
Updated the SessionSnodeKit to migration it's data from YDB to GRDB
Updated the SessionSnodeKit to use GRDB throughout it's logic
