perf annotate-data: Show first-level children by default in TUI

perf annotate-data: Show first-level children by default in TUI

Now default is to fold everything but it only shows the name of the
top-level data type which is not very useful.  Instead just expand the
top level entry so that it can show the layout at a higher level.

  Annotate type: 'struct task_struct' (4 samples)
        Percent     Offset       Size  Field
  -      100.00          0       9792  struct task_struct {                           ◆
  +        0.50          0         24      struct thread_info     thread_info;        ▒
           0.00         24          4      unsigned int   __state;                    ▒
           0.00         32          8      void*  stack;                              ▒
  +        0.00         40          4      refcount_t     usage;                      ▒
           0.00         44          4      unsigned int   flags;                      ▒
           0.00         48          4      unsigned int   ptrace;                     ▒
           0.00         52          4      int    on_cpu;                             ▒
  +        0.00         56         16      struct __call_single_node      wake_entry; ▒
           0.00         72          4      unsigned int   wakee_flips;                ▒
           0.00         80          8      long unsigned int      wakee_flip_decay_ts;▒
           0.00         88          8      struct task_struct*    last_wakee;         ▒
           0.00         96          4      int    recent_used_cpu;                    ▒
           0.00        100          4      int    wake_cpu;                           ▒
           0.00        104          4      int    on_rq;                              ▒
           0.00        108          4      int    prio;                               ▒
           0.00        112          4      int    static_prio;                        ▒
           0.00        116          4      int    normal_prio;                        ▒
           0.00        120          4      unsigned int   rt_priority;                ▒
  +        0.00        128        256      struct sched_entity    se;                 ▒
  +        0.00        384         48      struct sched_rt_entity rt;                 ▒
  +        0.00        432        224      struct sched_dl_entity dl;                 ▒
           0.00        656          8      struct sched_class*    sched_class;        ▒
  ...

Committer testing:

  # perf mem record -a sleep 5s
  # perf annotate --group --data-type=pthread_mutex_t

 Annotate type: 'pthread_mutex_t' (13 samples)
      Percent     Offset       Size  Field
-      100.00          0         40  pthread_mutex_t {                                ▒
-      100.00          0         40      struct __pthread_mutex_s       __data {      ▒
        39.45          0          4          int        __lock;                       ▒
         0.00          4          4          unsigned int       __count;              ▒
         7.80          8          4          int        __owner;                      ▒
         6.88         12          4          unsigned int       __nusers;             ▒
        45.87         16          4          int        __kind;                       ▒
         0.00         20          2          short int  __spins;                      ▒
         0.00         22          2          short int  __elision;                    ▒
+        0.00         24         16          __pthread_list_t   __list;               ▒
                                         };                                           ▒
         0.00          0          0      char[] __size;                               ▒
        39.45          0          8      long int       __align;

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: 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>
Link: https://lore.kernel.org/r/20240812194447.2049187-4-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>