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/citra_qt/main.ui

@@ -85,6 +85,7 @@
     <addaction name="action_Report_Compatibility"/>
     <addaction name="separator"/>
     <addaction name="action_Configure"/>
+    <addaction name="action_Cheats"/>
    </widget>
    <widget class="QMenu" name="menu_View">
     <property name="title">
@@ -227,6 +228,11 @@
     <string>Configure...</string>
    </property>
   </action>
+  <action name="action_Cheats">
+   <property name="text">
+    <string>Cheats...</string>
+   </property>
+  </action>
   <action name="action_Display_Dock_Widget_Headers">
    <property name="checkable">
     <bool>true</bool>