perf test: Add a new test for perf stat cgroup BPF counter

  $ sudo ./perf test -v each-cgroup
   96: perf stat --bpf-counters --for-each-cgroup test                 :
  --- start ---
  test child forked, pid 79600
  test child finished with 0
  ---- end ----
  perf stat --bpf-counters --for-each-cgroup test: Ok

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: Song Liu <songliubraving@fb.com>
Cc: bpf@vger.kernel.org
Link: https://lore.kernel.org/r/20220916184132.1161506-5-namhyung@kernel.org


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