Add initial snapshot support

[dlopes7]

This adds initial support for snapshot, the idea is:

If running on the OneAgent:

• Find the config directory
• Find the log directory by parsing installation.conf from the config directory
• Parse the oneagent_latest_snapshot.log from log_dir/plugin/oneagent_latest_snapshot.log

If running in dt-sdk run

• The user can OPTIONALLY pass a parameter to self.get_snapshot()
• If the parameter exists, we parse the file from that parameter
• If the parameter doesn't exist, we parse snapshot.json

Example usage:

      process_snapshot = self.get_snapshot()
      for entry in process_snapshot.entries:
          for process in entry.processes:
              if process.process_name in ("squid", "squid.exe")
                  self.extract_squid_metrics(process)