[xharness] Don't generate into the same directory/files for macOS Mod…

…ern and macOS Full. (xamarin#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.

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