Improve text-size detection in the case of PE and Mach-O files. In both
cases if a suitable `.text`-like section is not found then the text size
will be the sum of all segments with an executable flag.
Implement override mechanisms via command-line and/or env for the
following aspects:
* The maximum memory set by `test-harness`
* The timeout handled by `test-harness`
* The number of concurrent jobs to spawn while running `revng mass-testing run`
Giacomo Vercesi