Adding an empty process that is built and installed along with GCPW.
gcpw_extension.exe process is meant to be a service process that is
installed by gcp_setup.exe.

In this change;

An empty process with basic initialization is created
Self extracting module script is modified to include gcpw_extension.exe
Adds another event category called "GCPW Extension Events"

Bug: 1101590
Change-Id: I39f0e73d266c5328b4c18d348003a9109a55fe78
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2278588Reviewed-by: Rakesh Soma <rakeshsoma@google.com>
Reviewed-by: Nico Weber <thakis@chromium.org>
Commit-Queue: Yusuf Sengul <yusufsn@google.com>
Cr-Commit-Position: refs/heads/master@{#789533}