fix-tests (#140)

- downgrade unicorn to last working version
- update to new cp reg struct system
- remove nonexistent register (used to silently continue)
- fix partial unmap tests
    - InitializeSignalHandler() was moved out of the translator (almost 2.5 years ago), but the test code was never updated to manually call the function as it was changed to do in the real cpu context, so the tests just started failing.
    - by manually initializing the handler we no longer cause tests to fail.

Reviewed-on: https://git.ryujinx.app/projects/Ryubing/pulls/140

src/Ryujinx.Cpu/Signal/NativeSignalHandler.cs

@@ -53,7 +53,7 @@ namespace Ryujinx.Cpu.Signal
         public SignalHandlerRangeArray Ranges;
     }
 
-    static class NativeSignalHandler
+    public static class NativeSignalHandler
     {
         private static readonly nint _handlerConfig;
         private static nint _signalHandlerPtr;