Added a few interfaces for adding/deleting/replacing/saving cheats. The cheats list is guarded by a std::shared_mutex, and would only need a exclusive lock when it's being updated.
I marked the `Execute` function as `const` to avoid accidentally changing the internal state of the cheat on execution, so that execution can be considered a "read" operation which only needs a shared lock.
Whether a cheat is enabled or not is now saved by a special comment line `*citra_enabled`.
* 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
