perf trace: Add --summary-mode option

perf trace: Add --summary-mode option

The --summary-mode option will select how to show the syscall summary at
the end.  By default, it'll show the summary for each thread and it's
the same as if --summary-mode=thread is passed.

The other option is to show total summary, which is --summary-mode=total.
I'd like to have this instead of a separate option like --total-summary
because we may want to add a new summary mode (by cgroup) later.

  $ sudo ./perf trace -as --summary-mode=total sleep 1

   Summary of events:

   total, 21580 events

     syscall            calls  errors  total       min       avg       max       stddev
                                       (msec)    (msec)    (msec)    (msec)        (%)
     --------------- --------  ------ -------- --------- --------- ---------     ------
     epoll_wait          1305      0 14716.712     0.000    11.277   551.529      8.87%
     futex               1256     89 13331.197     0.000    10.614   733.722     15.49%
     poll                 669      0  6806.618     0.000    10.174   459.316     11.77%
     ppoll                220      0  3968.797     0.000    18.040   516.775     25.35%
     clock_nanosleep        1      0  1000.027  1000.027  1000.027  1000.027      0.00%
     epoll_pwait           21      0   592.783     0.000    28.228   522.293     88.29%
     nanosleep             16      0    60.515     0.000     3.782    10.123     33.33%
     ioctl                510      0     4.284     0.001     0.008     0.182      8.84%
     recvmsg             1434    775     3.497     0.001     0.002     0.174      6.37%
     write               1393      0     2.854     0.001     0.002     0.017      1.79%
     read                1063    100     2.236     0.000     0.002     0.083      5.11%
     ...

Reviewed-by: Howard Chu <howardchu95@gmail.com>
Acked-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Link: https://lore.kernel.org/r/20250205205443.1986408-5-namhyung@kernel.org
Signed-off-by: Namhyung Kim <namhyung@kernel.org>