Add NLS test scenario

[lbussell]

• Fixes Check for Windows NLS vs. ICU behavior differences in Globalization tests #6034

NLS is Windows-only, so I defined a completely separate scenario for it that runs only on Windows.

The test uses the recommended method for determining whether or not we're using ICU, and then validates some of the differences between NLS and ICU behavior based on what it finds.

For now, we will expect that NLS is used on all Nano Server images, and ICU is used on all Windows Server Core images. ICU has been the default on Server Core since .NET 7 and Server Core LTSC 2019. See https://learn.microsoft.com/en-us/dotnet/core/compatibility/globalization/7.0/icu-globalization-api for more context there.

[Copilot]

Copilot reviewed 5 out of 8 changed files in this pull request and generated no comments.

Files not reviewed (3)

• tests/Microsoft.DotNet.Docker.Tests/Microsoft.DotNet.Docker.Tests.csproj: Language not supported
• tests/Microsoft.DotNet.Docker.Tests/TestAppArtifacts/NLSTest.Dockerfile: Language not supported
• tests/Microsoft.DotNet.Docker.Tests/AspnetImageTests.cs: Evaluated as low risk

Comments suppressed due to low confidence (2)

tests/Microsoft.DotNet.Docker.Tests/TestScenarios/NLSScenario.cs:54

• Incorrect array initializer syntax. Use curly braces '{}' instead of square brackets '[]'.

string[] buildArgs = [

tests/Microsoft.DotNet.Docker.Tests/RuntimeImageTests.cs:52

• Ensure that the new VerifyNLSScenario method is covered by tests.

public async Task VerifyNLSScenario(ProductImageData imageData) =>