Adds a pair of options for Dexter that allow the user to specify a
timeout duration. These options are:
* --timeout-total: Times out if the total run-time of the debugger session
exceeds <timeout-total> seconds.
* --timeout-breakpoint: Times out if the time without hitting a
breakpoint exceeds <timeout-breakpoint> seconds.
Reviewed By: Orlando
Differential Revision: https://reviews.llvm.org/D145063
ee5617dc71