Create ARCodeWidget and GeckoCodeWidget once on startup rather than
every time a game is launched or shutdown.

In addition to losing focus on the tab (since the previous widget and
tab no longer existed), the behavior prior to this commit could cause a
crash if the user initiated a game shutdown and then opened a code edit
window since the AR/GeckoCodeWidget would get deleted in the meantime.

OnResetClicked and GenerateARCode appear to have been using the CPUThreadGuard in error.

RetroAchievements does not allow cheats such as Action Replay or Gecko in hardcore mode, for fairness.

At the end of each frame automatically update the Current Value for
visible table rows in the selected and visible CheatSearchWidget (if
any). Also update all Current Values in all CheatSearchWidgets when the
State changes to Paused.

Only updating visible table rows serves to minimize the performance cost
of this feature. If the user scrolls to an un-updated cell it will
promptly be updated by either the next VIEndFieldEvent or the State
transitioning to Paused.