perf list: Support filtering in JSON output

perf list: Support filtering in JSON output

Like regular output mode, it should honor command line arguments to
limit to a certain type of PMUs or events.

  $ perf list -j hw
  [
  {
          "Unit": "cpu",
          "Topic": "legacy hardware",
          "EventName": "branch-instructions",
          "EventType": "Kernel PMU event",
          "BriefDescription": "Retired branch instructions [This event is an alias of branches]",
          "Encoding": "cpu/event=0xc4\n/"
  },
  {
          "Unit": "cpu",
          "Topic": "legacy hardware",
          "EventName": "branch-misses",
          "EventType": "Kernel PMU event",
          "BriefDescription": "Mispredicted branch instructions",
          "Encoding": "cpu/event=0xc5\n/"
  },
  ...

Reviewed-by: Ian Rogers <irogers@google.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>