Settle a location for the log4j2.xml file

CLONED from SOLR-12008 since 12008 couldn't be closed.

As part of SOLR-11934 I started looking at log4j.properties files. Waaay back in 2015, the %C in "/solr/server/resources/log4j.properties" was changed to use %c, but the file in "solr/example/resources/log4j.properties" was not changed. That got me to looking around and there are a bunch of log4j.properties files:

./solr/core/src/test-files/log4j.properties
./solr/example/resources/log4j.properties
./solr/solrj/src/test-files/log4j.properties
./solr/server/resources/log4j.properties
./solr/server/scripts/cloud-scripts/log4j.properties
./solr/contrib/dataimporthandler/src/test-files/log4j.properties
./solr/contrib/clustering/src/test-files/log4j.properties
./solr/contrib/ltr/src/test-files/log4j.properties
./solr/test-framework/src/test-files/log4j.properties

Why do we have so many? After the log4j2 ticket gets checked in (SOLR-7887) I propose the logging configuration files get consolidated. The question is "how far"?

I at least want to get rid of the one in solr/example, users should use the one in server/resources. Having to maintain these two separately is asking for trouble.

markrmiller@gmail.com Do you have any wisdom on the properties file in server/scripts/cloud-scripts?

Anyone else who has a clue about why the other properties files were created, especially the ones in contrib?

And what about all the ones in various test-files directories? People didn't create them for no reason, and I don't want to rediscover that it's a real pain to try to re-use the one in server/resources for instance.