Silence slf4j noise on startup

[raboof]

In #28673 we fixed the following startup noise for tests:

SLF4J: A number (1) of logging calls during the initialization phase have been intercepted and are
SLF4J: now being replayed. These are subject to the filtering rules of the underlying logging system.
SLF4J: See also http://www.slf4j.org/codes.html#replay

I also regularly see this in example/quickstart/small 'regular' applications. Perhaps we can somehow write something to slf4j on/before startup for 'regular' actor systems as well?