test-dump-counters: Test dump-counters via unix-command socket

[awelzel]

Replaces https://github.com/OISF/suricata-verify/pull/1683

Changes since v4:

• Switch to af-packet source because using pcap blocks Suricata termination on Debian 10 and Ubuntu 20.04.

Changes since v3:

• Don't use ps, not available in CI everywhere.
• Invoke suricatasc with python3.

Changes since v2:

• Rewrote as shell script invoking suricatasc instead of using the suricatasc Python module
• Set rule-files.0=/dev/null to prevent loading of rules
• Set a BPF filter to make capture on lo unlikely

Test for https://github.com/OISF/suricata/pull/10468

Ticket

Ticket: 6732

Redmine ticket: https://redmine.openinfosecfoundation.org/issues/6732