Implement a "Pause Emulation" option & hotkey (#2428)

* Add a "Pause Emulation" option and hotkey

Closes Ryujinx#1604

* Refactoring how pause is handled

* Applied suggested changes from review

* Applied suggested fixes

* Pass correct suspend type to threads for suspend/resume

* Fix NRE after stoping emulation

* Removing SimulateWakeUpMessage call after resuming emulation

* Skip suspending non game process

* Pause the tickCounter in the ExecutionContext

* Refactoring tickCounter pause/resume as suggested

* Fix Config migration to add pause hotkey

* Fixed pausing only application threads

* Fix exiting emulator while paused

* Avoid pause/resume while already paused/resumed

* Cleanup unused code

* Avoid restarting audio if stopping emulation while in pause.

* Added suggested changes

* Fix ConfigurationState

Ryujinx.Common/Configuration/Hid/KeyboardHotkeys.cs

@@ -5,5 +5,6 @@
         public Key ToggleVsync { get; set; }
         public Key Screenshot { get; set; }
         public Key ShowUi { get; set; }
+        public Key Pause { get; set; }
     }
 }