[tests] Assert.Inconclusive() tests with http errors

[jonathanpeppers]

MSBuild tests using DownloadedCache can randomly fail with HTTP errors such as:

System.Net.Http.HttpRequestException : Response status code does not indicate success: 504 (Gateway Time-out).
Stack trace
at System.Net.Http.HttpResponseMessage.EnsureSuccessStatusCode()
at Xamarin.ProjectTools.DownloadedCache.GetAsFile(String url, String filename) in /Users/runner/work/1/s/android/src/Xamarin.Android.Build.Tasks/Tests/Xamarin.ProjectTools/Common/DownloadedCache.cs:line 39
at Xamarin.ProjectTools.BuildItem.<>c__DisplayClass70_0.<set_WebContent>b__0() in /Users/runner/work/1/s/android/src/Xamarin.Android.Build.Tasks/Tests/Xamarin.ProjectTools/Common/BuildItem.cs:line 309
at Xamarin.ProjectTools.XamarinProject.<>c.<Save>b__110_0(BuildItem s) in /Users/runner/work/1/s/android/src/Xamarin.Android.Build.Tasks/Tests/Xamarin.ProjectTools/Common/XamarinProject.cs:line 455
at System.Collections.Generic.List`1.AddRange(IEnumerable`1 collection)
at Xamarin.ProjectTools.XamarinProject.Save(Boolean saveProject) in /Users/runner/work/1/s/android/src/Xamarin.Android.Build.Tasks/Tests/Xamarin.ProjectTools/Common/XamarinProject.cs:line 455
at Xamarin.ProjectTools.ProjectBuilder.Save(XamarinProject project, Boolean doNotCleanupOnUpdate, Boolean saveProject) in /Users/runner/work/1/s/android/src/Xamarin.Android.Build.Tasks/Tests/Xamarin.ProjectTools/Common/ProjectBuilder.cs:line 98
at Xamarin.ProjectTools.ProjectBuilder.Build(XamarinProject project, Boolean doNotCleanupOnUpdate, String[] parameters, Boolean saveProject, Dictionary`2 environmentVariables) in /Users/runner/work/1/s/android/src/Xamarin.Android.Build.Tasks/Tests/Xamarin.ProjectTools/Common/ProjectBuilder.cs:line 128
at Xamarin.Android.Build.Tests.BindingBuildTest.BindngFilterUnsupportedNativeAbiLibraries(AndroidRuntime runtime) in /Users/runner/work/1/s/android/src/Xamarin.Android.Build.Tasks/Tests/Xamarin.Android.Build.Tests/BindingBuildTest.cs:line 411
at System.RuntimeMethodHandle.InvokeMethod(Object target, Void** arguments, Signature sig, Boolean isConstructor)
at System.Reflection.MethodBaseInvoker.InvokeDirectByRefWithFewArgs(Object obj, Span`1 copyOfArgs, BindingFlags invokeAttr)

Let's call Assert.Inconclusive() when we catch such exceptions, so that the test is marked as inconclusive instead of failed.

We also log information about the exception.

[Copilot]

Pull request overview

This PR improves test reliability by handling transient HTTP errors gracefully. When tests download resources using DownloadedCache, transient network failures (timeouts, gateway errors, etc.) will now mark tests as inconclusive rather than failed, with detailed logging to aid debugging.

Key changes:

• Added try-catch block to handle HttpRequestException with transient error filtering
• Implemented IsTransientError() method to identify recoverable HTTP errors (504, 408, 502, 503)
• Added comprehensive logging before marking tests inconclusive