Minor, "cosmetic" change, let's push it to 8.3.0

I'm not sure if we shouldn't go slf4j (MIT licence simple facade, I'd say "standard" in projects, which offers more flexibility and we already do have it as dependency because some dependencies already required it) instead of quite limited System.Logger, which seems to be intended more for internal use even, as per https://openjdk.org/jeps/264:

Non-Goals:

• It is not a goal to define a general-purpose interface for logging. The service interface contains only the minimal set of methods that the JDK needs for its own usage.

Consider using MDC (https://logback.qos.ch/manual/mdc.html; for JID, sesssion-id, connection-id)

In the end I think we should go with slf4j as it gives more flexibility and it's basically a standard. What's more, it would give us nice and easy integration with Loki via: https://loki4j.github.io/loki-logback-appender/.

I started exploring OpenRewrite (https://docs.openrewrite.org/) to handle the migration though recipes to migrate away from JUL are either non-existent or utterly rudimentary.

tigase-utils and tigase-xmltools migrated to System.Logger (instead of slf4j) as those are tiny libraries with very minimal logging thus avoiding additional dependency is convenient (and slf4j can be used as provider if present, otherwise JUL will be used as a default fallback). Remaining projects should use slf4j as it gives more flexibility and additional features.