Add support for sound backends & some miniaudio changes (#4978)

Miniaudio now runs everything in a separate audio thread - this uses boost::asio's io_context.
Our miniaudio implementation is now also much simplified - it does not use its own resource manager or device. This might end up being stupid if sounds don't work after changing output device or locking or w/e
I've made the sound controller into an interface, meaning we can support multiple sound backends in Chatterino. I've added a Null sound backend that disables all sound. A QMediaPlayer or QSoundEffect or Qt backend could be added.
Miniaudio might idle & disable the device now too, not sure

I've added some unrelated changes in the form of a new setting type, and a new setting page helper function for it, which will hopefully make adding new enum settings easier in the future.
This setting stores its value as a string instead of an int, and uses magic_enum to convert between that string value and its enum value.

src/Application.hpp

@@ -22,6 +22,7 @@ class HighlightController;
 class HotkeyController;
 class IUserDataController;
 class UserDataController;
+class ISoundController;
 class SoundController;
 class ITwitchLiveController;
 class TwitchLiveController;
@@ -67,6 +68,7 @@ public:
     virtual FfzBadges *getFfzBadges() = 0;
     virtual SeventvBadges *getSeventvBadges() = 0;
     virtual IUserDataController *getUserData() = 0;
+    virtual ISoundController *getSound() = 0;
     virtual ITwitchLiveController *getTwitchLiveController() = 0;
     virtual ImageUploader *getImageUploader() = 0;
     virtual SeventvAPI *getSeventvAPI() = 0;
@@ -109,7 +111,7 @@ public:
     FfzBadges *const ffzBadges{};
     SeventvBadges *const seventvBadges{};
     UserDataController *const userData{};
-    SoundController *const sound{};
+    ISoundController *const sound{};
 
 private:
     TwitchLiveController *const twitchLiveController{};
@@ -172,6 +174,7 @@ public:
         return this->seventvBadges;
     }
     IUserDataController *getUserData() override;
+    ISoundController *getSound() override;
     ITwitchLiveController *getTwitchLiveController() override;
     ImageUploader *getImageUploader() override
     {
@@ -200,6 +203,14 @@ private:
         return *t;
     }
 
+    template <typename T,
+              typename = std::enable_if_t<std::is_base_of<Singleton, T>::value>>
+    T &emplace(T *t)
+    {
+        this->singletons_.push_back(std::unique_ptr<T>(t));
+        return *t;
+    }
+
     NativeMessagingServer nmServer{};
 };