GitLab

Add support in 'perf list' to output tool internal events, currently
only 'duration_time'.

Committer testing:

  $ perf list dur*

  List of pre-defined events (to be used in -e):

    duration_time                                      [Tool event]

  Metric Groups:

  $ perf list sw

  List of pre-defined events (to be used in -e):

    alignment-faults                                   [Software event]
    bpf-output                                         [Software event]
    context-switches OR cs                             [Software event]
    cpu-clock                                          [Software event]
    cpu-migrations OR migrations                       [Software event]
    dummy                                              [Software event]
    emulation-faults                                   [Software event]
    major-faults                                       [Software event]
    minor-faults                                       [Software event]
    p...