Prior to this commit, the Couchbase auto-configuration would use the
bucket credentials when RBAC is configured. This commit ensures that
RBAC is used in that case.

This commit also adds new configuration properties to customize the
bootstrap ports for Couchbase:

* `spring.couchbase.env.bootstrap.http-direct-port`
* `spring.couchbase.env.bootstrap.http-ssl-port`

Fixes gh-19393