perf script: Add 'cgroup' field for output

perf script: Add 'cgroup' field for output

There's no field for the cgroup, let's add one.  To do that, users need to
specify --all-cgroup option for perf record to capture the cgroup info.

  $ perf record --all-cgroups -- true

  $ perf script -F comm,pid,cgroup
            true 337112  /user.slice/user-657345.slice/user@657345.service/...
            true 337112  /user.slice/user-657345.slice/user@657345.service/...
            true 337112  /user.slice/user-657345.slice/user@657345.service/...
            true 337112  /user.slice/user-657345.slice/user@657345.service/...

If it's recorded without the --all-cgroups, it'd complain.

  $ perf script -F comm,pid,cgroup
  Samples for 'cycles:u' event do not have CGROUP attribute set. Cannot print 'cgroup' field.
  Hint: run 'perf record --all-cgroups ...'

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: https://lore.kernel.org/r/20230126213610.3381147-1-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>