Performance hit due to unneeded UPDATE to increment "Concurrency" counter when there are no saga state changes

[ramonsmits]

When there are no saga state changes we will still do an UPDATE that increments the "Concurrency" column

https://github.com/Particular/NServiceBus.Persistence.Sql/blob/9affa576774df39fe4b746409329eb181e1dbab6/src/SqlPersistence/Saga/SqlDialect_MsSqlServer.cs#L71-L78

This causes an unneeded roundtrip to the database. Network IO is very slow thus has a performance impact

Considerations:

• Currently, we only have pessimistic locking. With pessimistic locking there is no need at all to increment the counter.
• With optimistic concurrency control, there is a side effect as multiple messages are processed. This likely is not a problem but there can be race conditions of emitted messages due to concurrent processing when falsely assuming ordered processing. However, this can also happen with pessimistic locking but less likely.