GPU: Implement guest driver profile and deduce texture handler sizes.

src/video_core/engines/maxwell_3d.h

@@ -1306,6 +1306,8 @@ public:
         return regs.tex_cb_index;
     }
 
+    VideoCore::GuestDriverProfile& AccessGuestDriverProfile() override;
+
     /// Memory for macro code - it's undetermined how big this is, however 1MB is much larger than
     /// we've seen used.
     using MacroMemory = std::array<u32, 0x40000>;