Fix: DHCPv6_am returns Reply instead of Solicit for DHCP6_Request

[AbhishekPandey1998]

Summary

Fixes the bug where DHCPv6_am.make_reply() would return a DHCP6_Solicit message in response to a DHCP6_Request, which violates RFC 8415. The correct behavior is to send a DHCP6_Reply.

Changes

• Replaced DHCP6_Solicit with DHCP6_Reply in the handler for msgtype == 3
• Added a test case to verify correct behavior

Closes: #4689

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 80.55%. Comparing base (b54fdb7) to head (c70f15c).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4799      +/-   ##
==========================================
+ Coverage   80.08%   80.55%   +0.46%     
==========================================
  Files         365      365              
  Lines       89027    89027              
==========================================
+ Hits        71296    71712     +416     
+ Misses      17731    17315     -416     

Files with missing lines	Coverage Δ
scapy/layers/dhcp6.py	73.89% <100.00%> (-12.37%)	⬇️

... and 38 files with indirect coverage changes

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.