Use Private Nuget Feed for OneBranch

[nibanks]

Description

Updates internal builds to use nuget.config to use internal mirror instead of nuget.org directly.

Testing

Created internal draft PR to trigger pipeline: https://mscodehub.visualstudio.com/msquic/_build/results?buildId=531354&view=logs&j=4e010f65-6a42-5318-8120-b81b51c2abd2&t=abd3eb9e-9a6d-521e-c133-9e198ddfd123

Documentation

N/A

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 86.50%. Comparing base (9c4dceb) to head (4c112a8).
Report is 4 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4557      +/-   ##
==========================================
- Coverage   87.20%   86.50%   -0.71%     
==========================================
  Files          56       56              
  Lines       17354    17354              
==========================================
- Hits        15134    15012     -122     
- Misses       2220     2342     +122     

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