Replace BitUtils with C++20: Counting Zeroes

With the upgrade to C++20, std::countl_zero and std::countr_zero can replace these home-spun implementations from the BitUtil.h library.

Source/Core/Core/PowerPC/Interpreter/Interpreter_Integer.cpp

@@ -209,7 +209,7 @@ void Interpreter::cmpl(UGeckoInstruction inst)
 
 void Interpreter::cntlzwx(UGeckoInstruction inst)
 {
-  rGPR[inst.RA] = u32(Common::CountLeadingZeros(rGPR[inst.RS]));
+  rGPR[inst.RA] = u32(std::countl_zero(rGPR[inst.RS]));
 
   if (inst.Rc)
     Helper_UpdateCR0(rGPR[inst.RA]);