Potential durable state performance improvements

[johanandren]

The durable state has a two-step operation when updating the state, first picking up a new global unique seq number and then the actual insert/update (see JdbcDurableStateStore. I think we could, at least for some of the databases, fold that into a single insert/update referencing the sequence number generator.

Could also be worth making that update into a prepared statement rather than an ad hoc statement for each insert/update.

[patriknw]

Sounds like a good improvement.