Convert bulk update/delete to new execution model

Convert bulk update/delete to new execution model

This reorganizes the BulkUD model in sqlalchemy.orm.persistence
to be based on the CompileState concept and to allow plain
update() / delete() to be passed to session.execute() where
the ORM synchronize session logic will take place.
Also gets "synchronize_session='fetch'" working with horizontal
sharding.

Adding a few more result.scalar_one() types of methods
as scalar_one() seems like what is normally desired.

Fixes: #5160
Change-Id: I8001ebdad089da34119eb459709731ba6c0ba975