perf trace: Allow configuring if the syscall duration should be printed

  # perf config trace.show_duration=no
  # perf config -l | grep trace
  trace.default_events=/home/acme/git/perf/tools/perf/examples/bpf/augmented_raw_syscalls.o
  trace.show_zeros=true
  trace.show_duration=no
  # trace -e *sleep sleep 1
     0.000 sleep/8729 nanosleep(rqtp: 0x7ffcb0b4c940, rmtp: 0) = 0
  # perf config trace.show_duration=yes
  # trace -e *sleep sleep 1
     0.000 (1000.212 ms): sleep/8735 nanosleep(rqtp: 0x7ffca15fa770, rmtp: 0) = 0
  #

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Luis Cláudio Gonçalves <lclaudio@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: https://lkml.kernel.org/n/tip-2c7h1m8fhzb9puxtj9nlevi8@git.kernel.org


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>