[RFC] make docker termination timeout configurable

[sryza]

Summary & Motivation

Not a part of the codebase I am super familiar with, but makes it possible to configure the timeout when canceling a run launched by the docker run launcher.

A couple questions:

• Does it make sense to set a termination timeout on the docker executor?
• If so, is there somewhere that we test step termination

How I Tested These Changes

Changelog

Insert changelog entry or delete this section.