Add CodeQL suppression for DefaultAzureCredential use in Production

[paulmedynski]

• Adhere to strict CodeQL suppression format.

[Copilot]

Pull Request Overview

This PR adds a CodeQL suppression comment to address a security analysis warning about DefaultAzureCredential instantiation in production code. The change restructures the comment placement to comply with CodeQL's requirement that suppression comments appear on the same line as the flagged code.

• Moved CodeQL suppression comment to the same line as the DefaultAzureCredential instantiation
• Added explanatory documentation about CodeQL suppression placement requirements
• Split the credential instantiation and return statement for better code organization

Comments suppressed due to low confidence (1)

src/Microsoft.Data.SqlClient/src/Microsoft/Data/SqlClient/ActiveDirectoryAuthenticationProvider.cs:599

• The variable name 'cred' is too abbreviated and unclear. Consider using a more descriptive name like 'credential' or 'azureCredential' to improve code readability.

                DefaultAzureCredential cred = new(defaultAzureCredentialOptions); // CodeQL [SM05137] See above for justification.

[codecov]

Codecov Report

❌ Patch coverage is 28.57143% with 10 lines in your changes missing coverage. Please review.
✅ Project coverage is 64.58%. Comparing base (18becfe) to head (40359b1).
⚠️ Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
.../Data/SqlClient/ManagedSni/SniTcpHandle.netcore.cs	16.66%	10 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3542      +/-   ##
==========================================
+ Coverage   60.32%   64.58%   +4.25%     
==========================================
  Files         270      270              
  Lines       62098    62110      +12     
==========================================
+ Hits        37463    40113    +2650     
+ Misses      24635    21997    -2638     

Flag	Coverage Δ
netcore	67.85% <28.57%> (+5.70%)	⬆️
netfx	64.47% <100.00%> (+0.01%)	⬆️

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[cheenamalhotra]

This will be back-ported to release branches as well?

[paulmedynski]

Yes, we can backport for the ReceiveTimeout change. The CodeQL part is benign on non-default branches AFAIK.