This diff factors out the "business logic" in resolveKeyserverSessionInvalidation, making it possible to use the function with the new identity service-based keyserver auth.
SQLiteDataHandler on native is the only callsite that remains outside of KeyserverConnectionHandler. It needs to remain special-cased because SQLiteDataHandler does its work before KeyserverConnectionHandler is rendered, since KeyserverConnectionHandler depends on data being loaded into Redux. In a later diff I'll address how SQLiteDataHandler will work in the multi-keyserver world, but the short story is that it will need to re-load data from the backup service rather than from the authoritative keyserver.
NOTE: The recovery logic in SQLiteDataHandler is broken here because it doesn't directly dispatch setNewSession. This was broken in D10952, and will be fixed in a later diff. I decided not to fix this up earlier because it would require introducing code that would later be ripped out.
Depends on D11224