Bump Microsoft.NET.Test.Sdk and System.Collections.Immutable

Bumps [Microsoft.NET.Test.Sdk](https://github.com/microsoft/vstest) and [System.Collections.Immutable](https://github.com/dotnet/corefx). These dependencies needed to be updated together.

Updates `Microsoft.NET.Test.Sdk` from 17.8.0 to 17.11.0
- [Release notes](https://github.com/microsoft/vstest/releases)
- [Changelog](https://github.com/microsoft/vstest/blob/main/docs/releases.md)
- [Commits](microsoft/vstest@v17.8.0...v17.11.0)

Updates `System.Collections.Immutable` from 1.2.0 to 1.5.0
- [Release notes](https://github.com/dotnet/corefx/releases)
- [Commits](https://github.com/dotnet/corefx/commits)

---
updated-dependencies:
- dependency-name: Microsoft.NET.Test.Sdk
  dependency-type: direct:production
  update-type: version-update:semver-minor
- dependency-name: System.Collections.Immutable
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Directory.Packages.props

@@ -4,7 +4,7 @@
         <PackageVersion Include="BenchmarkDotNet" Version="0.13.10" />
         <PackageVersion Include="coverlet.collector" Version="6.0.2" />
         <PackageVersion Include="Microsoft.AspNetCore.TestHost" Version="8.0.0" />
-        <PackageVersion Include="Microsoft.NET.Test.Sdk" Version="17.8.0" />
+        <PackageVersion Include="Microsoft.NET.Test.Sdk" Version="17.11.0" />
         <PackageVersion Include="System.Buffers" Version="4.5.1" />
         <PackageVersion Include="System.Memory" Version="4.5.5" />
         <PackageVersion Include="System.Collections.Immutable" Version="1.2.0" />