perf report: Sort child tasks by tid

perf report: Sort child tasks by tid

Commit 91e467bc568f ("perf machine: Use hashtable for machine
threads") made the iteration of thread tids unordered. The perf report
--tasks output now shows child threads in an order determined by the
hashing. For example, in this snippet tid 3 appears after tid 256 even
though they have the same ppid 2:

```
$ perf report --tasks
%      pid      tid     ppid  comm
         0        0       -1 |swapper
         2        2        0 | kthreadd
       256      256        2 |  kworker/12:1H-k
    693761   693761        2 |  kworker/10:1-mm
   1301762  1301762        2 |  kworker/1:1-mm_
   1302530  1302530        2 |  kworker/u32:0-k
         3        3        2 |  rcu_gp
...
```

The output is easier to read if threads appear numerically
increasing. To allow for this, read all threads into a list then sort
with a comparator that orders by the child task's of the first common
parent. The list creation and deletion are created as utilities on
machine.  The indentation is possible by counting the number of
parents a child has.

With this change the output for the same data file is now like:
```
$ perf report --tasks
%      pid      tid     ppid  comm
         0        0       -1 |swapper
         1        1        0 | systemd
       823      823        1 |  systemd-journal
       853      853        1 |  systemd-udevd
      3230     3230        1 |  systemd-timesyn
      3236     3236        1 |  auditd
      3239     3239     3236 |   audisp-syslog
      3321     3321        1 |  accounts-daemon
...
```

Signed-off-by: Ian Rogers <irogers@google.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Yang Jihong <yangjihong1@huawei.com>
Cc: Oliver Upton <oliver.upton@linux.dev>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/r/20240301053646.1449657-2-irogers@google.com