Add CI support for testing VMs with net devices

[alexandruag]

The current integration testing logic does not have first class support for network devices.

• The start_vmm_process function from test_run_reference_vmm.py file should allow configuring a VM with net support as well.
• Let's add auxiliary functionality for creating, configuring, and tearing down TAP interfaces on the host. This will be called as part of the test logic.
• Finally, add a test that starts a VM with a net device attached, configures it within the guest, and then uses commands/applications to ensure communication is functional.

An example of configuring communication with the VM via a network device backed by a TAP interface is available in the description of #49.