Provide startup time in UserSessionProvider independent of Infinispan,
cleanup code that is not necessary for the map storage as it isn't using Clustering.
Move classes to the legacy module.
Closes#12972
* 99% 1:1 wrapper of the underlying quarkus gelf extension.
* excluded `filter-stack-trace` and `stack-trace-throwable-reference` options for now, as they are either undocumented on the quarkus side or not important imo.
* added docs and examples for Graylog and ELK stack
* NOT added an automated test, as this is really a 1:1 wrapper around the extension, Test setup would be cumbersome, test would take too much time and tests are done in quarkus itself.
Closes#12125
