Fix net462 build failures by adding missing System.IO.Pipelines and System.Threading.Channels packages (#4881)

* Initial plan

* Initial analysis of net462 build failures

Co-authored-by: DrewScoggins <[email protected]>

* Add System.IO.Pipelines and System.Threading.Channels packages for .NET Framework targets

Co-authored-by: DrewScoggins <[email protected]>

---------

Co-authored-by: copilot-swe-agent[bot] <[email protected]>
Co-authored-by: DrewScoggins <[email protected]>

Author: Copilot

src/benchmarks/micro/MicroBenchmarks.csproj

@@ -93,6 +93,8 @@
     <PackageReference Include="System.Memory" Version="4.5.5" />
     <PackageReference Include="System.Numerics.Vectors" Version="4.5.0" />
     <PackageReference Include="System.Threading.Tasks.Extensions" Version="4.5.4" />
+    <PackageReference Include="System.IO.Pipelines" Version="$(SystemVersion)" />
+    <PackageReference Include="System.Threading.Channels" Version="$(SystemVersion)" />
   </ItemGroup>
   <ItemGroup Condition="'$(TargetFrameworkIdentifier)' == '.NETCoreApp' And '$(_TargetFrameworkVersionWithoutV)' &lt; '10.0'">
     <PackageReference Include="System.Diagnostics.DiagnosticSource" Version="$(SystemVersion)" />