Remove package source mapping to enable VMR backflow (#14233)

* Initial plan

* Remove package source mapping and suppress NU1507

Co-authored-by: mmitche <8725170+mmitche@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: mmitche <8725170+mmitche@users.noreply.github.com>

Author: Copilot

NuGet.config

@@ -16,62 +16,6 @@
     <!-- CsWin32 dailies -->
     <add key="winsdk" value="https://pkgs.dev.azure.com/azure-public/winsdk/_packaging/CI/nuget/v3/index.json" />
   </packageSources>
-  <packageSourceMapping>
-    <clear />
-    <packageSource key="dotnet-eng">
-      <package pattern="microsoft.*" />
-      <package pattern="runtime.*" />
-      <package pattern="system.*" />
-    </packageSource>
-    <packageSource key="dotnet-libraries">
-      <package pattern="System.Runtime.CompilerServices.Unsafe" />
-    </packageSource>
-    <packageSource key="dotnet-libraries-transport">
-      <package pattern="Microsoft.Private.Intellisense" />
-    </packageSource>
-    <packageSource key="dotnet-tools">
-      <package pattern="microsoft.*" />
-      <package pattern="MicroBuild.Core.Sentinel" />
-      <package pattern="sn" />
-    </packageSource>
-    <packageSource key="dotnet9">
-      <package pattern="microsoft.*" />
-      <package pattern="runtime.*" />
-      <package pattern="system.*" />
-    </packageSource>
-    <packageSource key="dotnet9-transport">
-      <package pattern="microsoft.*" />
-      <package pattern="system.*" />
-    </packageSource>
-    <packageSource key="dotnet10">
-      <package pattern="microsoft.*" />
-      <package pattern="runtime.*" />
-      <package pattern="system.*" />
-    </packageSource>
-    <packageSource key="dotnet10-transport">
-      <package pattern="microsoft.*" />
-      <package pattern="system.*" />
-    </packageSource>
-    <packageSource key="dotnet11">
-      <package pattern="microsoft.*" />
-      <package pattern="runtime.*" />
-      <package pattern="system.*" />
-    </packageSource>
-    <packageSource key="dotnet11-transport">
-      <package pattern="microsoft.*" />
-      <package pattern="system.*" />
-    </packageSource>
-    <packageSource key="winsdk">
-      <package pattern="microsoft.*" />
-    </packageSource>
-    <!-- This is the default feed -->
-    <packageSource key="dotnet-public">
-      <package pattern="microsoft.*" />
-      <package pattern="runtime.*" />
-      <package pattern="system.*" />
-      <package pattern="*" />
-    </packageSource>
-  </packageSourceMapping>
   <disabledPackageSources>
     <clear />
   </disabledPackageSources>

eng/Analyzer.props

@@ -6,6 +6,9 @@
     <!-- Only upgrade NuGetAudit warnings to errors for official builds. -->
     <WarningsNotAsErrors Condition="'$(OfficialBuild)' != 'true'">$(WarningsNotAsErrors);NU1901;NU1902;NU1903;NU1904</WarningsNotAsErrors>
 
+    <!-- Suppress NU1507 (Package source mapping is not compatible with VMR backflow operations) -->
+    <NoWarn>$(NoWarn);NU1507</NoWarn>
+
     <EnforceCodeStyleInBuild>true</EnforceCodeStyleInBuild>
 
     <!--