No service restart is required for Solr to pick up the new logging settings
Since this setting is trying to find long running search queries, logs for troubleshooting should be collected no sooner than 30 minutes after reproducing the issue.
Debug logging will list all queries active and completed every 10 seconds
Restarting the services will also cause EDR to replace the existing log4j2.xml with the log4j2.xml.template
For Solr debugging to survive a restart of the services the log4j2.xml.template can be modified