New task spawner

To test the IP run:

vivado -mode batch -source scripts/run_tests.tcl -tclargs N_RUNS RUN_LENGTH SEED TEST_PATH

Where:

• N_RUNS is the number of simulation runs
• RUN_LENGTH is the length in nanoseconds of each simulation
• SEED is the seed to use for the simulation
• TEST_PATH is the path to the output directory