feat: add simple PMC counters support

[kavirajk]

Part of this issue #92

Changes

1. Add Pmc counters of basic hardware/software counters (cycles,
   instructions and context-switches)
2. Add apis (open, close, reset, enable, disable) for those PMC counters
3. Also integrated with file-perf benchmark to show it's usefulness.

counters

ec2-numa-dev$ ./build/release/bin/file-perf --filename /dev/shm/testfile --print-counters --pmc
...
,  "pmc": {
    "valid": true,
    "scaled": false,
    "cycles": 351131134388,
    "instructions": 180409144759,
    "context_switches": 12217432,
    "ipc": 0.5138,
    "cycles_per_io": 67772.3,
    "instructions_per_io": 34821.0
  }
...

[praktika-gh]

Workflow [PR], commit [7034a52]