This is basically a pytest re-implementation of the get_ports.sh script.
The main difference is that ports are assigned on a module basis, rather
than a directory basis. Module is the new atomic unit for parallel
execution, therefore it needs to have unique ports to avoid collisions.
Each module gets its ports through the env fixture which is updated with
ports and other module-specific variables.
(cherry picked from commit 0061758156)
aa199e2726