feat(networksecurity): update library

[scotthart]

PiperOrigin-RevId: 919268561

[gemini-code-assist]

Code Review

This pull request introduces several new services to the Network Security API C++ client library, including Address Group, DNS Threat Detector, Firewall Activation, and Intercept. It generates the corresponding client, connection, stub, and decorator classes, and updates the documentation and configuration files. The review feedback highlights critical compilation errors in address_group_client.cc where iterators are incorrectly assigned to a RepeatedPtrField, and a formatting issue in CHANGELOG.md with an empty markdown link placeholder.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.71%. Comparing base (a393a27) to head (b7297ec).
⚠️ Report is 5 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #16122      +/-   ##
==========================================
- Coverage   92.71%   92.71%   -0.01%     
==========================================
  Files        2353     2353              
  Lines      219451   219451              
==========================================
- Hits       203474   203470       -4     
- Misses      15977    15981       +4     

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