Continuing work on account migration

* Prune all folders, messages & attachments that won't migrate
* Clean up SSL/TLS values for better connection results & security
* Move account setup lookup code to AccountSettingsUtils to share it
* Cleanup config/auto-rotation settings to prevent relaunch of
  auto-discover or account check (from exchange).
* A couple of other very small fixes

Bug: 2065528
1 file changed