Add a bin script to handle signals with parallel_tests

[ArturT]

Tested locally and signals are passed:

KNAPSACK_PRO_CI_NODE_INDEX=0 Received signal INT in bin/parallel_tests, terminating the Knapsack Pro process with TERM
KNAPSACK_PRO_CI_NODE_INDEX=0 Waiting for the Knapsack Pro process with PID 73665 to terminate
KNAPSACK_PRO_CI_NODE_INDEX=1 Received signal INT in bin/parallel_tests, terminating the Knapsack Pro process with TERM
KNAPSACK_PRO_CI_NODE_INDEX=1 Waiting for the Knapsack Pro process with PID 73666 to terminate