Add GUC update_process_title to control whether 'ps' display is updated

doc/src/sgml/config.sgml

src/backend/bootstrap/bootstrap.c

src/backend/commands/async.c

src/backend/postmaster/autovacuum.c

src/backend/postmaster/pgarch.c

src/backend/postmaster/pgstat.c

src/backend/postmaster/postmaster.c

src/backend/postmaster/syslogger.c

src/backend/storage/lmgr/lock.c

src/backend/tcop/postgres.c

src/backend/utils/misc/guc.c

src/backend/utils/misc/postgresql.conf.sample

src/backend/utils/misc/ps_status.c

src/include/utils/ps_status.h