shader: Move loop safety tests to code emission

src/shader_recompiler/backend/glsl/emit_context.h

@@ -153,6 +153,8 @@ public:
     std::vector<TextureImageDefinition> images;
     std::array<std::array<GenericElementInfo, 4>, 32> output_generics{};
 
+    u32 num_safety_loop_vars{};
+
     bool uses_y_direction{};
     bool uses_cc_carry{};