This allows disabling the check on startup if one knows the database won't be reachable.

It also currently defaults to being disabled when a dialect is set explicitly (`quarkus.hibernate-orm.dialect=something`), in order to work around problems we have with correctly detecting the version on some databases that we don't have tests for (unsupported ones).

This is a workaround for #43703 and #42255, but is not a fix: we will need Hibernate ORM 7.0 for an actual fix that makes database version checks work correctly even on Azure SQL Server or CockroachDB.