[xharness] Don't generate into the same directory/files for macOS Modern and macOS Full. (#9121)

* [xharness] Don't generate into the same directory/files for macOS Modern and macOS Full.

This meant that we were overwriting some generated files, which meant that we
were executing the Modern set of tests instead of the Full set of tests for at
least some configurations.

* Add a few ignored tests to the System.Configuration test now that we actually run it.

Author: rolfbjarne

tests/bcl-test/macOSFull-xammac_net_4_5_System.Configuration_test.dll.ignore

@@ -5,4 +5,22 @@ MonoTests.System.Configuration.AppSettingsSectionTest.TestFile
 
 # Expected: not null
 # But was:  null
-MonoTests.System.Configuration.ConfigurationManagerTest.TestConnectionStringRetrieval
+MonoTests.System.Configuration.ConfigurationManagerTest.TestConnectionStringRetrieval
+
+# The UnixSignalTest breaks NullReferenceException handling in the runtime.
+# Any NRE will deadlock the process after this test, so just skip it.
+MonoTests.Mono.Unix.UnixSignalTest
+
+# Needs RabbitMQ:
+#     System.TypeInitializationException : The type initializer for '...' threw an exception.
+#     ----> System.IO.FileNotFoundException : Could not load the file 'Mono.Messaging.RabbitMQ, Version=4.0.0.0, Culture=neutral, PublicKeyToken=0738eb9f132ed756'.
+MonoTests.System.Messaging.TransactionMessageTest
+MonoTests.System.Messaging.AdminTest
+MonoTests.System.Messaging.AsyncPeekTest
+MonoTests.System.Messaging.AsyncReceiveTest
+MonoTests.System.Messaging.BasicMessagingTest
+MonoTests.System.Messaging.PeekTest
+MonoTests.System.Messaging.SelectorTest
+
+# System.ArgumentException : The value's length for key 'data source' exceeds it's limit of '128'.
+DbLinqTest.DataContextTest.Ctor_FileOrServerOrConnectionIsFilename

tests/xharness/Microsoft.DotNet.XHarness.iOS.Shared/TestImporter/Templates/Managed/XamariniOSTemplate.cs

@@ -680,7 +680,7 @@ async Task<GeneratedProjects> GenerateMacTestProjectsAsync (IEnumerable<(string
 				if (!projectDefinition.Validate ())
 					throw new InvalidOperationException ("xUnit and NUnit assemblies cannot be mixed in a test project.");
 				// generate the required type registration info
-				var generatedCodeDir = Path.Combine (GeneratedCodePathRoot, projectDefinition.Name, "mac");
+				var generatedCodeDir = Path.Combine (GeneratedCodePathRoot, projectDefinition.Name, platform.ToString ());
 				Directory.CreateDirectory (generatedCodeDir);
 				var registerTypePath = Path.Combine (generatedCodeDir, "RegisterType-mac.cs");