[counters] Improve mono counters API and integrate it to the log profiler

Improvement of the mono counters API:
 - now support differents types, units
 - retrocompatible with the previous API
 - update some gc counters to use this new API
 - multiple data sources : performance counters, system data (cpu, memory, ...)

Integration to the log profiler:
 - sampling of the counters in the log profiler
 - sampling interval as profiler's parameter
 - updated mprof-report to print them