fix(engines): the dpkt engine applies the first PCAP-NG interface's linktype and timestamp resolution to every frame #1379

dpkt.pcapng.Reader (dpkt 1.9.8) reads only the first Interface Description Block of a PCAP-NG file. Its constructor loops until it hits an IDB and then breaks (site-packages/dpkt/pcapng.py:589-603), and that one IDB supplies the linktype and timestamp resolution for every packet. Found while cross-reviewing #1370.

Consequence for extract(engine='dpkt'): in a capture whose interfaces differ, for example test.pcapng with 2 IDBs in section 1 and another in section 2, frames on any later interface get interface 0's linktype and if_tsresol. That can mean wrong timestamps, or a frame dissected as the wrong link type. The default engine reads every IDB.

Needed:

• Measure. Build or find a capture whose IDBs differ in linktype or if_tsresol, compare dpkt against the default engine, and report the differences.
• Then pick a fix: either feed per-interface linktype and resolution from pcapkit's own PCAP-NG reading into the dpkt engine, or document the limitation beside docs(engines): the dpkt engine silently drops PCAP-NG Simple Packet Blocks #1361's note in 3rdparty.rst.

Blocked on #1370 (same 3rdparty.rst section and engines/dpkt.py docstring) and #1377 (same engines/dpkt.py).