fix(internet): IGMPv2 and IGMPv3 names carry no version #2558

From the 2026-11-01 conventions audit, re-verified on 73add05a3. protocol-family-grouping.rst, "Canonical Names": a versioned protocol's display name includes its version (the owner's stated preference on #2444, not a settled rule). IGMPv1 is exempt: RFC 1112 names it plain IGMP.

• IGMP.name in pcapkit/protocols/internet/igmp.py is defined once, on the family base, so the IGMPv1, IGMPv2 and IGMPv3 classes all report 'Internet Group Management Protocol', while alias is 'IGMP', 'IGMPv2' and 'IGMPv3' and id() is versioned.
• L2TPv2, IPv4 and IPv6 already carry the version in name; HTTP is a documented exception. fix(internet): IGMPv3 and IGMP base id() disagree with the family-grouping ruling #2512 aligned id() and alias on IGMP, not name.

Fix: give IGMPv2 and IGMPv3 their own name ("... version 2", "... version 3", per RFC 2236 and RFC 3376), leave IGMPv1's, and test all three values.
Blocked: #2542 renames the IGMP member classes in the same modules; unblocks when it merges (gh pr view 2542 --json state -q .state prints MERGED).