[dotnet] Call monovm_initialize before mono_jit_init

Those are called respectively inside `xamarin_vm_initialize` and
`xamarin_bridge_initialize` functions.

This fix the **AppContext.GetData always return null for iOS** issue
dotnet/runtime#50290

Added unit tests to ensure `AppContext.GetData` can read back the values
we're providing at startup.

runtime/monotouch-main.m

@@ -402,11 +402,10 @@ - (void) memoryWarning: (NSNotification *) sender
 	xamarin_initialize_cocoa_threads (NULL);
 #endif
 
-	xamarin_bridge_initialize ();
-
 #if DOTNET
 	xamarin_vm_initialize ();
 #endif
+	xamarin_bridge_initialize ();
 
 	xamarin_initialize ();
 	DEBUG_LAUNCH_TIME_PRINT ("\tmonotouch init time");

tests/linker/CommonLinkAnyTest.cs

@@ -42,5 +42,14 @@ public static void Bug7114 ([CallerFilePath] string filePath = null)
 			Assert.IsNotNull (filePath, "CallerFilePath");
 		}
 
+#if NET
+		[Test]
+		public void AppContextGetData ()
+		{
+			// https://github.com/dotnet/runtime/issues/50290
+			Assert.IsNotNull (AppContext.GetData ("APP_PATHS"), "APP_PATHS");
+			Assert.IsNotNull (AppContext.GetData ("PINVOKE_OVERRIDE"), "PINVOKE_OVERRIDE");
+		}
+#endif
 	}
 }