For Postgres:
- Drop Unique constraint on `keyname` and make primary key
- Change type of `value` from BYTEA to TEXT and drop its default
- Make `value` nullable to sync with MySQL/SQLite
MySQL:
- Change exptime from DATETIME to TIMESTAMP
MySQL/SQLite:
- Make 'exptime' not nullable
Bug: T230428
Bug: T164898
Change-Id: Iab9de8a1bb2cb01b6e3e69e66f1bbe089d53d0a7
