video_core/ast: Make ShowCurrentState() take a string_view instead of std::string

Allows the function to be non-allocating in terms of the output string.

src/video_core/shader/ast.h

@@ -332,7 +332,7 @@ public:
 
     void Decompile();
 
-    void ShowCurrentState(std::string state);
+    void ShowCurrentState(std::string_view state);
 
     void SanityCheck();