binary search tool: Change verify_level to boolean

Previously, the user could run multiple levels of verification. This
would essentially repeat verification multiple times. It's unsure why a
user would want to set verify_level to any value other than 0 or 1. Thus
verify_level is more appropriate as a boolean.

TEST=Run unit tests

Change-Id: Id8832c54e2733881bf23f48af2a3b4c294117d1c
Reviewed-on: https://chrome-internal-review.googlesource.com/272766
Commit-Ready: Cassidy Burden <cburden@google.com>
Tested-by: Cassidy Burden <cburden@google.com>
Reviewed-by: Caroline Tice <cmtice@google.com>
4 files changed