Move partial unmap handler to the native signal handler (#3437)

* Initial commit with a lot of testing stuff.

* Partial Unmap Cleanup Part 1

* Fix some minor issues, hopefully windows tests.

* Disable partial unmap tests on macos for now

Weird issue.

* Goodbye magic number

* Add COMPlus_EnableAlternateStackCheck for tests

`COMPlus_EnableAlternateStackCheck` is needed for NullReferenceException handling to work on linux after registering the signal handler, due to how dotnet registers its own signal handler.

* Address some feedback

* Force retry when memory is mapped in memory tracking

This case existed before, but returning `false` no longer retries, so it would crash immediately after unprotecting the memory... Now, we return `true` to deliberately retry.

This case existed before (was just broken by this change) and I don't really want to look into fixing the issue right now. Technically, this means that on guest code partial unmaps will retry _due to this_ rather than hitting the handler. I don't expect this to cause any issues.

This should fix random crashes in Xenoblade Chronicles 2.

* Use IsRangeMapped

* Suppress MockMemoryManager.UnmapEvent warning

This event is not signalled by the mock memory manager.

* Remove 4kb mapping

ARMeilleure/Signal/WindowsSignalHandlerRegistration.cs

@@ -1,9 +1,10 @@
 using System;
+using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
 
 namespace ARMeilleure.Signal
 {
-    class WindowsSignalHandlerRegistration
+    unsafe class WindowsSignalHandlerRegistration
     {
         [DllImport("kernel32.dll")]
         private static extern IntPtr AddVectoredExceptionHandler(uint first, IntPtr handler);
@@ -11,6 +12,14 @@ namespace ARMeilleure.Signal
         [DllImport("kernel32.dll")]
         private static extern ulong RemoveVectoredExceptionHandler(IntPtr handle);
 
+        [DllImport("kernel32.dll", SetLastError = true, CharSet = CharSet.Ansi)]
+        static extern IntPtr LoadLibrary([MarshalAs(UnmanagedType.LPStr)] string lpFileName);
+
+        [DllImport("kernel32.dll", CharSet = CharSet.Ansi, ExactSpelling = true, SetLastError = true)]
+        private static extern IntPtr GetProcAddress(IntPtr hModule, string procName);
+
+        private static IntPtr _getCurrentThreadIdPtr;
+
         public static IntPtr RegisterExceptionHandler(IntPtr action)
         {
             return AddVectoredExceptionHandler(1, action);
@@ -20,5 +29,17 @@ namespace ARMeilleure.Signal
         {
             return RemoveVectoredExceptionHandler(handle) != 0;
         }
+
+        public static IntPtr GetCurrentThreadIdFunc()
+        {
+            if (_getCurrentThreadIdPtr == IntPtr.Zero)
+            {
+                IntPtr handle = LoadLibrary("kernel32.dll");
+
+                _getCurrentThreadIdPtr = GetProcAddress(handle, "GetCurrentThreadId");
+            }
+
+            return _getCurrentThreadIdPtr;
+        }
     }
 }