RD DXIL Disassembly use DxOp enum values instead of string comparison

Added "dxOpFunctionNames" array to assert that the function name is as expected

Author: Zorro666

renderdoc/driver/shaders/dxil/dxil_bytecode.h

@@ -570,6 +570,7 @@ enum class DXOp : uint32_t
   SampleCmpBias = 255,
   StartVertexLocation = 256,
   StartInstanceLocation = 257,
+  NumOpCodes = 258,
 };
 
 enum class AtomicBinOpCode : uint32_t