Enable ThreadAbort with CET enabled via the QueueUserAPC2 (#70803)

This change makes ThreadAbort work when CET is enabled. Instead of
thread redirection, it uses the new user mode APC mechanism to get a
thread to a handler and then throws the ThreadAbortException from there
if the thread was interrupted at a safe location.

I have verified it works using mdbg tests and also by manual testing in
the Visual Studio 2022 using a test app that creates an instance of
classes with properties containing infinite loop, wait on a lock, wait
on a handle, infinite loop inside of a lock and infinite loop in
finally.
For the testing, I've enabled this separately from the CET so that the
missing support for CET in the debugger code doesn't cause troubles.

So we could enable this without CET enabled too, but I'd prefer doing
that separately.

src/coreclr/vm/threads.h

@@ -2215,6 +2215,7 @@ class Thread
     {
         SuspendForGC,
         SuspendForDebugger,
+        ThreadAbort,
     };
 
     bool InjectActivation(ActivationReason reason);