Use infra.libs.log in builder_alerts.
Use infra.libs.log in builder_alerts.

This causes builder_alerts to
a) Use a common logging format; and
b) Print a reasonable amount of logging (verified locally)

R=ojan@chromium.org, pgervais@chromium.org
BUG=429875

Review URL: https://codereview.chromium.org/708673002

nicko96/Chrome-Infra,nicko96/Chrome-Infra,nicko96/Chrome-Infra,nicko96/Chrome-Infra,nicko96/Chrome-Infra