This cl does the following things:

0) Implements a skeleton of incident_helper
1) Implements FileSection class which calls incident_helper to parse
   file content to protobuf
2) Adds Kernel Wake Sources to incident.proto and makes it parsed by
   FileSection
3) Adds basic gtests to test FdBuffer, io_utils, FileSection
implementation

Bug: 62923266
Bug: 62926061
Test: manual - push incidentd, incident_helper and incident to my device
      and verify kernel wakeup sources file is able to be parsed.
Change-Id: I2aa6b6158d962ce70e6fa6c8a9c42213a45ff41c