[dotnet] Add test project templates for all Apple platforms

[jonathanpeppers]

Summary

Add dotnet new test project templates for all Apple platforms, equivalent to what was done for Android in dotnet/android@885dd60.

Modeled after jonathanpeppers/iOSDotNetTest.

New templates

Short name	Platform	TFM
iostest	iOS	net10.0-ios
maccatalysttest	Mac Catalyst	net10.0-maccatalyst
tvostest	tvOS	net10.0-tvos
macostest	macOS	net10.0-macos

Usage:

dotnet new iostest -n MyTests
dotnet run --project MyTests

Each template creates an MSTest-based test project that runs tests inside the proper UIKit/AppKit run loop, displaying results in a native UI. This is needed because Apple platform tests must run inside a real application process.

Key design decisions

• Platform-appropriate entry points: iOS and Mac Catalyst use the UIKit SceneDelegate pattern. tvOS uses the older AppDelegate+Window pattern (no SceneDelegate support). macOS uses AppKit with NSApplication.
• MtouchInterpreter=all set globally: Instead of setting this workaround in each template, it is now set in Xamarin.Shared.props when EnableMSTestRunner=true, so any MSTest runner project on Apple platforms automatically gets the interpreter enabled.
• GenerateTestingPlatformEntryPoint=false: Required because our templates provide a custom Main() entry point and MSTest SDK would otherwise generate a conflicting one.
• Template tests updated: Added all 4 templates to TemplateTest.cs to verify they build correctly.

[jonathanpeppers]

I'm still testing this, I don't like the GetResults target, for example and there is logic in the template that should be in the workload.

[rolfbjarne]

There's a warning when building the tvOS test template:

This call site is reachable on: 'tvOS' 13.0 and later. 'UIWindow' is obsoleted on: 'tvos' 26.0 and later (Use the 'UIWindowScene' overload instead.).

There's also a number of warnings when building a maccatalyst template - but not the new one, so it feels unrelated, but on the other hand it's not a problem I've seen before, and it's too much of a coincidence that it happens in a PR that adds new templates...

Xamarin.Tests.TemplateTest.CreateAndBuildProjectTemplate(maccatalysttest-csharp): Build warnings:
    Microsoft.ApplicationInsights.Extensibility.Implementation.Authentication.ReflectionCredentialEnvelope.AzureCore.BuildDelegateAccessTokenToAuthToken(): Unrecognized value passed to the parameter 'typeName' of method 'System.Type.GetType(String)'. It's not possible to guarantee the availability of the target type.
    Microsoft.ApplicationInsights.Extensibility.Implementation.Authentication.ReflectionCredentialEnvelope.AzureCore.BuildDelegateAccessTokenToAuthToken(): Using member 'System.Linq.Expressions.Expression.Property(Expression, String)' which has 'RequiresUnreferencedCodeAttribute' can break functionality when trimming application code. Creating Expressions requires unreferenced code because the members being referenced by the Expression may be trimmed.
    Microsoft.ApplicationInsights.Extensibility.Implementation.Authentication.ReflectionCredentialEnvelope.AzureCore.BuildDelegateAccessTokenToAuthToken(): Using member 'System.Linq.Expressions.Expression.Property(Expression, String)' which has 'RequiresUnreferencedCodeAttribute' can break functionality when trimming application code. Creating Expressions requires unreferenced code because the members being referenced by the Expression may be trimmed.
[...]

[jonathanpeppers]

It seems like the dotnet new tvos template has the same warning about UIWindow. I could fix it in both templates, but I don't have a device to manually test it stil works.

ApplicationInsights is a dependency of MSTest and AppInsights has trimmer warnings. Copilot says MacCatalyst is doing SdkOnly mode, and the other platforms None -- I could make $(EnableMSTestRunner) default to $(SuppressTrimAnalysisWarnings)=true for now?

[vs-mobiletools-engineering-service2]

✅ [CI Build #a3dc29b] Build passed (Build packages) ✅

Pipeline on Agent
Hash: a3dc29b2907d73b4a7c122b27e2293a18cc69ff2 [PR build]

[vs-mobiletools-engineering-service2]

✅ [CI Build #a3dc29b] Build passed (Detect API changes) ✅

Pipeline on Agent
Hash: a3dc29b2907d73b4a7c122b27e2293a18cc69ff2 [PR build]

[vs-mobiletools-engineering-service2]

✅ API diff for current PR / commit

NET (empty diffs)

• iOS: vsdrops gist ( No breaking changes )
• tvOS: vsdrops gist ( No breaking changes )
• MacCatalyst: vsdrops gist ( No breaking changes )
• macOS: vsdrops gist ( No breaking changes )

✅ API diff vs stable

NET (empty diffs)

• iOS: vsdrops gist ( No breaking changes )
• tvOS: vsdrops gist ( No breaking changes )
• MacCatalyst: vsdrops gist ( No breaking changes )
• macOS: vsdrops gist ( No breaking changes )

ℹ️ Generator diff

Generator Diff: vsdrops (html) vsdrops (raw diff) gist (raw diff) - Please review changes)

Pipeline on Agent
Hash: a3dc29b2907d73b4a7c122b27e2293a18cc69ff2 [PR build]

[vs-mobiletools-engineering-service2]

✅ [CI Build #a3dc29b] Build passed (Build macOS tests) ✅

Pipeline on Agent
Hash: a3dc29b2907d73b4a7c122b27e2293a18cc69ff2 [PR build]