Add CheatEngine and support for Gateway cheats (#4406)

* Add CheatEngine; Add support for Gateway cheats; Add Cheat UI

* fix a potential crash on some systems

* fix substr with negative length

* Add Joker to the NonOp comp handling

* Fixup JokerOp

* minor fixup in patchop; add todo for nested loops

* Add comment for PadState member variable in HID

* fix: stol to stoul in parsing cheat file

* fix misplaced parsing of values; fix patchop code

* add missing break

* Make read_func and write_func a template parameter

src/core/cheats/cheat_base.cpp

@@ -0,0 +1,9 @@
+// Copyright 2018 Citra Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#include "core/cheats/cheat_base.h"
+
+namespace Cheats {
+CheatBase::~CheatBase() = default;
+} // namespace Cheats