Distributor: Add request_timeout function

[cbonaudo]

As discussed with Ignition, a request_timeout function can be useful as a timeout-able alternative to the request fn. It seems to work as is ("proven" by the tests), but I am open to suggestions of improvements or anything. Thanks for your time.

Checklist

• [x] tests are passing with cargo test.
• [x] tests and/or benchmarks are included
• [x] documentation is changed or added
• [x] commit message is clear