Support RavenDB 6

[tmasternak]

Describe the feature.

RavenDB 6 released Oct 2, 2023. We want the persisted to support that version.

Additional Context

• https://github.com/Particular/NServiceBus.RavenDB/pull/1333
• https://github.com/Particular/NServiceBus.RavenDB/pull/1319

[DavidBoike]

Observations from the task force that updated ServiceControl to RavenDB 6.2 in https://github.com/Particular/ServiceControl/pull/4484:

• The primary differences that affected ServiceControl were:
  • A few instances in the Client API of int becoming long
  • The Corax search engine is now available to replace Lucene, but Lucene is still supported. Persistence appears to only have 1 index used by Outbox, but for the persistence we are a guest in the database and should allow the administrator to decide what indexing strategy to use. We should split out Outbox tests with test cases to ensure both Lucene and Corax work correctly, however.
  • Changes that only affected the Docker container, not important here
• RavenDB uses product versions, not necessarily SemVer. Each Major.Minor pair is a "product version" and there may be breaking changes between them. Some Major.Minor pairs are declared LTS releases. Updating the client version to a newer product version but talking to an older server product version is not supported. See their backward compatibility statements.
  • Given this, there doesn't seem to be much reason to update the persistence to newer versions unless the product version is an LTS release.
  • Bumping the version up to a new product band can probably only be done in a major version of the persistence, as you would be cutting off support for a server version by doing that. An update to RavenDB 6.2 would therefore be a major change.

These changes would test the upper bounds of a small task given the release must be a major, requiring extra work for documentation, samples, and upgrade guides.