perf annotate: Fix --group behavior when leader has no samples

perf annotate: Fix --group behavior when leader has no samples

When --group option is used, it should display all events together.  But
the current logic only checks if the first (leader) event has samples or
not.  Let's check the member events as well.

Also it missed to put the linked samples from member evsels to the
output RB-tree so that it can be displayed in the output.

For example, take a look at this example.

  $ ./perf evlist
  cpu/mem-loads,ldlat=30/P
  cpu/mem-stores/P
  dummy:u

It has three events but 'path_put' function has samples only for
mem-stores (second) event.

  $ sudo ./perf annotate --stdio -f path_put
   Percent |      Source code & Disassembly of kcore for cpu/mem-stores/P (2 samples, percent: local period)
  ----------------------------------------------------------------------------------------------------------
           : 0                0xffffffffae600020 <path_put>:
      0.00 :   ffffffffae600020:       endbr64
      0.00 :   ffffffffae600024:       nopl    (%rax, %rax)
     91.22 :   ffffffffae600029:       pushq   %rbx
      0.00 :   ffffffffae60002a:       movq    %rdi, %rbx
      0.00 :   ffffffffae60002d:       movq    8(%rdi), %rdi
      8.78 :   ffffffffae600031:       callq   0xffffffffae614aa0
      0.00 :   ffffffffae600036:       movq    (%rbx), %rdi
      0.00 :   ffffffffae600039:       popq    %rbx
      0.00 :   ffffffffae60003a:       jmp     0xffffffffae620670
      0.00 :   ffffffffae60003f:       nop

Therefore, it didn't show up when --group option is used since the
leader ("mem-loads") event has no samples.  But now it checks both
events.

Before:
  $ sudo ./perf annotate --stdio -f --group path_put
  (no output)

After:
  $ sudo ./perf annotate --stdio -f --group path_put
   Percent                 |      Source code & Disassembly of kcore for cpu/mem-loads,ldlat=30/P, cpu/mem-stores/P, dummy:u (0 samples, percent: local period)
  -------------------------------------------------------------------------------------------------------------------------------------------------------------
                           : 0                0xffffffffae600020 <path_put>:
      0.00    0.00    0.00 :   ffffffffae600020:       endbr64
      0.00    0.00    0.00 :   ffffffffae600024:       nopl    (%rax, %rax)
      0.00   91.22    0.00 :   ffffffffae600029:       pushq   %rbx
      0.00    0.00    0.00 :   ffffffffae60002a:       movq    %rdi, %rbx
      0.00    0.00    0.00 :   ffffffffae60002d:       movq    8(%rdi), %rdi
      0.00    8.78    0.00 :   ffffffffae600031:       callq   0xffffffffae614aa0
      0.00    0.00    0.00 :   ffffffffae600036:       movq    (%rbx), %rdi
      0.00    0.00    0.00 :   ffffffffae600039:       popq    %rbx
      0.00    0.00    0.00 :   ffffffffae60003a:       jmp     0xffffffffae620670
      0.00    0.00    0.00 :   ffffffffae60003f:       nop

Committer testing:

Before:

  root@number:~# perf annotate --group --stdio2 clear_page_erms
  root@number:~#

After:

  root@number:~# perf annotate --group --stdio2 clear_page_erms
  Samples: 125  of events 'cpu_atom/mem-loads,ldlat=30/P, cpu_atom/mem-stores/P, dummy:u', 4000 Hz, Event count (approx.): 13198416, [percent: local period]
  clear_page_erms() /proc/kcore
  Percent                      0xffffffff990c6cc0 <clear_page_erms>:
                                 endbr64
                                 movl    $0x1000,%ecx
                                 xorl    %eax,%eax
     0.00  100.00    0.00        rep     stosb %al, (%rdi)
                               ← retq
                                 int3
                                 int3
                                 int3
                                 int3
                                 nop
                                 nop
  root@number:~#

Reported-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lore.kernel.org/lkml/20240807061555.1642669-1-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>