[FBE] Split accounts.db into two DE/CE databases

Previously the database lived in /data/system/user/X/accounts.db.
It is now split into two databases:
 - DE database(/data/system_de/X/accounts_de.db) is opened when the user is
   running in the locked state. It contains the following tables:
      -- Grants, Shared_Accounts, Debug_Table, Meta.
      -- Accounts table only contains name/type/_id
 - CE database (/data/system_ce/X/accounts_ce.db) is opened when the user is
   unlocked. It contains remaining tables:
      -- Authtokens, Extras, Accounts

CE database is attached to the DE database by using ATTACH DATABASE command.
AccountManager code interacts through a single interface of DeDatabaseHelper,
which includes DE, and CE when the user is unlocked.

Bug: 26279712
Change-Id: I66555b46bdc16fa4a6093470d2500af09d1fbf25