feat: add Network Traffic (.pcap) extractor to scalibr embeddedfs

[messiawrq-design]

Description

Closes #1901

This PR introduces the embeddedfs/nettraffic extractor for .pcap and .pcapng files.
It fulfills the requirement to scan network capture artifacts for sensitive information, credentials, and potential C2 traffic payload leaks.

Implementation Details:

• Integrated gopacket library to parse .pcap and .pcapng streams.
• Reconstructs packet payloads (TCP/UDP) and stores them virtually in common.EmbeddedDirFS for subsequent SCALIBR secrets and vulnerability detectors.
• Naming convention uses: <PROTOCOL>_<PROTOCOL>_<SRC_IP>_<SRC_PORT>_to_<DST_IP>_<DST_PORT>.txt to allow precise incident response correlation.
• Validated via make test over the entire extractor/filesystem/list and embeddedfs package structure.

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Bounty Payout Note:
If this contribution is eligible for an open-source bounty or reward program under Google/OSV-SCALIBR initiatives, please route the bounty allocation to the following Solana address:
6sF8p22Gg83NKTJ6dvya7Srv4USCniZnP47DwQwK7Mtp

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[messiawrq-design]

I signed it!