DBOS should support transactional steps for databases _other than_ Postgres

[chrisalbright]

I understand why DBOS uses Postgres, and it's a great system. I am not able to leverage it however because we run our major systems on Oracle. We can use Postgres for DBOS itself, but without Transactional Steps we lose a lot of the benefits it provides.

[devhawk]

TxStep is a pattern that can be implemented w/o any changes to the core DBOS library. But we haven't really documented the pattern, just the implementation of the pattern.