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/singletons/Settings.hpp

@@ -12,6 +12,7 @@
 #include "controllers/logging/ChannelLog.hpp"
 #include "controllers/moderationactions/ModerationAction.hpp"
 #include "controllers/nicknames/Nickname.hpp"
+#include "controllers/sound/ISoundController.hpp"
 #include "singletons/Toasts.hpp"
 #include "util/RapidJsonSerializeQString.hpp"
 #include "util/StreamerMode.hpp"
@@ -557,6 +558,12 @@ public:
     ChatterinoSetting<std::vector<QString>> enabledPlugins = {
         "/plugins/enabledPlugins", {}};
 
+    // Advanced
+    EnumStringSetting<SoundBackend> soundBackend = {
+        "/sound/backend",
+        SoundBackend::Miniaudio,
+    };
+
 private:
     ChatterinoSetting<std::vector<HighlightPhrase>> highlightedMessagesSetting =
         {"/highlighting/highlights"};