perf list: Add JSON output option

Output events and metrics in a JSON format by overriding the print
callbacks. Currently other command line options aren't supported and
metrics are repeated once per metric group.

Committer testing:

  $ perf list cache

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

    L1-dcache-load-misses                              [Hardware cache event]
    L1-dcache-loads                                    [Hardware cache event]
    L1-dcache-prefetches                               [Hardware cache event]
    L1-icache-load-misses                              [Hardware cache event]
    L1-icache-loads                                    [Hardware cache event]
    branch-load-misses                                 [Hardware cache event]
    branch-loads                                       [Hardware cache event]
    dTLB-load-misses                                   [Hardware cache event]
    dTLB-loads                                         [Hardware cache event]
    iTLB-load-misses                                   [Hardware cache event]
    iTLB-loads                                         [Hardware cache event]
  $ perf list --json cache
  [
  {
          "Unit": "cache",
          "EventName": "L1-dcache-load-misses",
          "EventType": "Hardware cache event"
  },
  {
          "Unit": "cache",
          "EventName": "L1-dcache-loads",
          "EventType": "Hardware cache event"
  },
  {
          "Unit": "cache",
          "EventName": "L1-dcache-prefetches",
          "EventType": "Hardware cache event"
  },
  {
          "Unit": "cache",
          "EventName": "L1-icache-load-misses",
          "EventType": "Hardware cache event"
  },
  {
          "Unit": "cache",
          "EventName": "L1-icache-loads",
          "EventType": "Hardware cache event"
  },
  {
          "Unit": "cache",
          "EventName": "branch-load-misses",
          "EventType": "Hardware cache event"
  },
  {
          "Unit": "cache",
          "EventName": "branch-loads",
          "EventType": "Hardware cache event"
  },
  {
          "Unit": "cache",
          "EventName": "dTLB-load-misses",
          "EventType": "Hardware cache event"
  },
  {
          "Unit": "cache",
          "EventName": "dTLB-loads",
          "EventType": "Hardware cache event"
  },
  {
          "Unit": "cache",
          "EventName": "iTLB-load-misses",
          "EventType": "Hardware cache event"
  },
  {
          "Unit": "cache",
          "EventName": "iTLB-loads",
          "EventType": "Hardware cache event"
  }
  ]
  $
Signed-off-by: Ian Rogers <irogers@google.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Caleb Biggers <caleb.biggers@intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kajol Jain <kjain@linux.ibm.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Leo Yan <leo.yan@linaro.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Perry Taylor <perry.taylor@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ravi Bangoria <ravi.bangoria@amd.com>
Cc: Rob Herring <robh@kernel.org>
Cc: Sandipan Das <sandipan.das@amd.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Weilin Wang <weilin.wang@intel.com>
Cc: Xin Gao <gaoxin@cdjrlc.com>
Cc: Xing Zhengjun <zhengjun.xing@linux.intel.com>
Link: http://lore.kernel.org/lkml/20221114210723.2749751-11-irogers@google.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/Documentation/perf-list.txt

@@ -43,6 +43,10 @@ Print deprecated events. By default the deprecated events are hidden.
 Print PMU events and metrics limited to the specific PMU name.
 (e.g. --unit cpu, --unit msr, --unit cpu_core, --unit cpu_atom)
 
+-j::
+--json::
+Output in JSON format.
+
 [[EVENT_MODIFIERS]]
 EVENT MODIFIERS
 ---------------