perf ftrace: Add 'tail' option to --graph-opts

The 'graph-tail' option is to print function name as a comment at the end.
This is useful when a large function is mixed with other functions
(possibly from different CPUs).

For example,

$ sudo perf ftrace -- perf stat true
...
1) | get_unused_fd_flags() {
1) | alloc_fd() {
1) 0.178 us | _raw_spin_lock();
1) 0.187 us | expand_files();
1) 0.169 us | _raw_spin_unlock();
1) 1.211 us | }
1) 1.503 us | }

$ sudo perf ftrace --graph-opts tail -- perf stat true
...
1) | get_unused_fd_flags() {
1) | alloc_fd() {
1) 0.099 us | _raw_spin_lock();
1) 0.083 us | expand_files();
1) 0.081 us | _raw_spin_unlock();
1) 0.601 us | } /* alloc_fd */
1) 0.751 us | } /* get_unused_fd_flags */

Reviewed-by: Ian Rogers <irogers@google.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: Changbin Du <changbin.du@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt (VMware) <rostedt@goodmis.org>
Link: https://lore.kernel.org/lkml/20240729004127.238611-2-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>