Add config option to enable packet dumping to PCAP file

[DL6ER]

What does this implement/fix?

Add new config option files.pcap to expose integrated packet (PCAP) dumping to a file. This PR also fixes a small issue with the hostname test failing in the most recent ftl-build containers.

Related issue or feature (if applicable): N/A

Pull request in docs with documentation (if applicable): N/A

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