GUC with PGC_BACKEND context should also be dispatched to QE (#7741)
GUC with PGC_BACKEND context should also be dispatched to QE (#7741)

PGC_BACKEND means GUC could be set through PGOPTIONS in libpq
which is the same as how we pass GUC from QD to QE.

Reviewed-by: Asim R P <24f343109504afa210657d296a0873118cbd2b97@pivotal.io>
greenplum-db/gpdb,lisakowen/gpdb,lisakowen/gpdb,xinzweb/gpdb,lisakowen/gpdb,jmcatamney/gpdb,50wu/gpdb,50wu/gpdb,jmcatamney/gpdb,lisakowen/gpdb,jmcatamney/gpdb,greenplum-db/gpdb,adam8157/gpdb,adam8157/gpdb,ashwinstar/gpdb,greenplum-db/gpdb,greenplum-db/gpdb,50wu/gpdb,xinzweb/gpdb,ashwinstar/gpdb,50wu/gpdb,greenplum-db/gpdb,ashwinstar/gpdb,xinzweb/gpdb,jmcatamney/gpdb,ashwinstar/gpdb,50wu/gpdb,adam8157/gpdb,xinzweb/gpdb,lisakowen/gpdb,ashwinstar/gpdb,greenplum-db/gpdb,adam8157/gpdb,adam8157/gpdb,50wu/gpdb,ashwinstar/gpdb,xinzweb/gpdb,xinzweb/gpdb,jmcatamney/gpdb,jmcatamney/gpdb,greenplum-db/gpdb,50wu/gpdb,adam8157/gpdb,ashwinstar/gpdb,xinzweb/gpdb,adam8157/gpdb,xinzweb/gpdb,ashwinstar/gpdb,greenplum-db/gpdb,adam8157/gpdb,lisakowen/gpdb,jmcatamney/gpdb,jmcatamney/gpdb,lisakowen/gpdb,lisakowen/gpdb,50wu/gpdb