This introduces a new timeout field for configuring the timeout period

for builds on CircleCI, Jenkins, and Travis-CI. This is used to ensure

that if a build takes too long, it can be retried by the review request

owner.
The field uses AmountSelectorWidget, configured to let users specify a

number and select "seconds", "minutes", "hours", or "Never" for the

timeout.

Unit tests passed.
Manually configured the timeouts and verified the configuration in

Status Updates.