Clean up the sampling profiler

- rename variables/fields names to match the code style (use
_underscore_names_)
- extract common property parsing in utils.cc
- fail to load profile file if any line is malformed
- added ProfileFile to manage the profile data generate in the previous
runs (replaces ProfileHelper and nests ProfileData)

Bug: 12877748
Change-Id: Ie7bda30bfdeb7e78534c986615b0649eac12a97b