Add promise wait timeout

[jgraichen]

This PR introduce a timeout capability to promises defaulting to 300 seconds. The timeout is required and cannot be zero.

[franzliedke]

Hmm... let's (ahem) sleep over this one for a bit. I just read too many bad things about Ruby's Timeout module:

• https://www.mikeperham.com/2015/05/08/timeout-rubys-most-dangerous-api/
• http://blog.headius.com/2008/02/rubys-threadraise-threadkill-timeoutrb.html
• https://jvns.ca/blog/2015/11/27/why-rubys-timeout-is-dangerous-and-thread-dot-raise-is-terrifying/

Most importantly, this one: https://vaneyckt.io/posts/the_disaster_that_is_rubys_timeout_method/ (That has a nice example that could help us find out whether Timeout.timeout causes problems with Restify as well.)

This might be a helpful, more positive, resource: https://github.com/ankane/the-ultimate-guide-to-ruby-timeouts

[jgraichen]

Interesting. No article seems to mention Thread#handle_interrupt.

[jgraichen]

I've made a new implementation based on an high-res timer interval that is used to pass the remaining time to subsequent operations. Running code such as promise code blocks will not be interrupted.