OpcodeDispatcher: Fixes SHLD by 16 behaviour

We were assuming that SHLD undefined behaviour matches SHL, but the
specification actually changes a `ge` comparison to `gt`, which means a
shift of 16 isn't UB!

Thanks to the impeccable @OFFTKP in #5842 for bringing this up as it took a bit
for me to figure out what was actually wrong here. I modified their
unittest to cover more just to ensure we don't break it.

FEXCore/Source/Interface/Core/OpcodeDispatcher.cpp

@@ -1526,7 +1526,7 @@ void OpDispatchBuilder::SHLDImmediateOp(OpcodeArgs) {
       Res = _Extr(OpSizeFromSrc(Op), Dest, Src, Size - Shift);
     }
 
-    CalculateFlags_ShiftLeftImmediate(OpSizeFromSrc(Op), Res, Dest, Shift);
+    CalculateFlags_ShiftLeftImmediate(OpSizeFromSrc(Op), Res, Dest, Shift, true);
     CalculateDeferredFlags();
     StoreResultGPR(Op, Res);
   } else if (Shift == 0 && Size == 32) {