Since spark.sql.hive.thriftServer.singleSession is a configuration of SQL component, this conf can be moved from SparkConf to StaticSQLConf.
When we introduced spark.sql.hive.thriftServer.singleSession, all the SQL configuration can be modified in different sessions. Later, static SQL configuration is added. It is a perfect fit for spark.sql.hive.thriftServer.singleSession. Previously, we did the same move for spark.sql.warehouse.dir from SparkConf to StaticSQLConf