Remove Log4jConfig junit extension in favor LoggerContextSource

The Log4JConfig JUnit extension was introduced by HIVE-24588 in order to facilitate running tests with a specific log4j2 configuration.

However, there is a very similar and seemingly more powerful JUnit extension in the official LOG4J2 release/repo, i.e., LoggerContextSource. 

The goal of this JIRA is to remove code related to Log4jConfig from Hive repo and replace its usages with LoggerContextSource. By doing this we reduce the maintenance overhead for the Hive community and reduce the dependencies to log4j-core.