[BOLT] Add value profiling to BOLT

Summary:
Add support for reading value profiling info from perf data.  This diff adds support in DataReader/DataAggregator for value profiling data.  Each event is recorded as two Locations (a PC and an address/value) and a count.

For now, I'm assuming that the value profiling data is in the same file as the usual BOLT profiling data.  Collecting both at the same time seems to work.

(cherry picked from FBD6076877)