perf top: Collapse and resort all evsels in a group

And link them, i.e. find the hist entries in the non-leader events and
link them to the ones in the leader.

This should be the same thing already done for the 'perf report' case,
but now we do it periodically.

With this in place we get percentages in from the second overhead column
on, not just on the first (the leader).

Try it using:

  perf top --stdio -e '{cycles,instructions}'

You should see something like:

   PerfTop:   20776 irqs/sec  kernel:68.7%  exact:  0.0% lost: 0/0 drop: 0/0 [cycles],  (all, 8 CPUs)
  ---------------------------------------------------------------------------------------------------

     4.44%   0.44%  [kernel]                 [k] do_syscall_64
     2.27%   0.17%  [kernel]                 [k] entry_SYSCALL_64
     1.73%   0.27%  [kernel]                 [k] syscall_return_via_sysret
     1.60%   0.91%  [kernel]                 [k] _raw_spin_lock_irqsave
     1.45%   3.53%  libglib-2.0.so.0.6000.4  [.] g_string_insert_unichar
     1.39%   0.21%  [kernel]                 [k] copy_user_enhanced_fast_string
     1.26%   1.15%  [kernel]                 [k] psi_task_change
     1.16%   0.14%  libpixman-1.so.0.38.0    [.] 0x000000000006f403
     1.00%   0.32%  [kernel]                 [k] __sched_text_start
     0.97%   2.11%  [kernel]                 [k] n_tty_write
     0.96%   0.04%  [kernel]                 [k] queued_spin_lock_slowpath
     0.93%   0.88%  [kernel]                 [k] menu_select
     0.87%   0.14%  [kernel]                 [k] try_to_wake_up
     0.77%   0.10%  libpixman-1.so.0.38.0    [.] 0x000000000006f40b
     0.73%   0.09%  libpixman-1.so.0.38.0    [.] 0x000000000006f413
     0.69%   0.48%  libc-2.29.so             [.] __memmove_avx_unaligned_erms
     0.68%   0.29%  [kernel]                 [k] _raw_spin_lock_irq
     0.61%   0.04%  libpixman-1.so.0.38.0    [.] 0x000000000006f423
     0.60%   0.37%  [kernel]                 [k] native_sched_clock
     0.57%   0.23%  [kernel]                 [k] do_idle
     0.57%   0.23%  [kernel]                 [k] __fget
     0.56%   0.30%  [kernel]                 [k] __switch_to_asm
     0.56%   0.00%  libc-2.29.so             [.] __memset_avx2_erms
     0.52%   0.32%  [kernel]                 [k] _raw_spin_lock
     0.49%   0.24%  [kernel]                 [k] n_tty_poll
     0.49%   0.54%  libglib-2.0.so.0.6000.4  [.] g_mutex_lock
     0.48%   0.62%  [kernel]                 [k] _raw_spin_unlock_irqrestore
     0.47%   0.27%  [kernel]                 [k] __switch_to
     0.47%   0.25%  [kernel]                 [k] pick_next_task_fair
     0.45%   0.17%  [kernel]                 [k] filldir64
     0.40%   0.16%  [kernel]                 [k] update_rq_clock
     0.39%   0.19%  [kernel]                 [k] enqueue_task_fair
  #

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lkml.kernel.org/n/tip-uw8cjeifxvjpkjp6x2iil0ar@git.kernel.org


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