Deprecate IDatabase::nextSequenceValue()

Deprecate IDatabase::nextSequenceValue()

It's often forgotten because MySQL and Sqlite don't use it, the only
users are PostgreSQL and Oracle. And when used, if inserts to multiple
tables are being done it's easy to get the ordering wrong.

This patch reimplements DatabasePostgres::insertId() in terms of PG's
lastval() function, and adds triggers to the Oracle schema to make it
work the same as the other databases.

Bug: T164900
Change-Id: Ib308190c52673a9266c8495a589ae644f9fbefce