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.

CHANGELOG.md

@@ -11,6 +11,7 @@
 - Minor: The `/usercard` command now accepts user ids. (#4934)
 - Minor: Add menu actions to reply directly to a message or the original thread root. (#4923)
 - Minor: The `/reply` command now replies to the latest message of the user. (#4919)
+- Minor: All sound capabilities can now be disabled by setting your "Sound backend" setting to "Null" and restarting Chatterino. (#4978)
 - Bugfix: Fixed an issue where certain emojis did not send to Twitch chat correctly. (#4840)
 - Bugfix: Fixed capitalized channel names in log inclusion list not being logged. (#4848)
 - Bugfix: Trimmed custom streamlink paths on all platforms making sure you don't accidentally add spaces at the beginning or end of its path. (#4834)
@@ -41,6 +42,7 @@
 - Bugfix: Fixed lookahead/-behind not working in _Ignores_. (#4965)
 - Bugfix: Fixed Image Uploader accidentally deleting images with some hosts when link resolver was enabled. (#4971)
 - Bugfix: Fixed rare crash with Image Uploader when closing a split right after starting an upload. (#4971)
+- Dev: Run miniaudio in a separate thread, and simplify it to not manage the device ourselves. There's a chance the simplification is a bad idea. (#4978)
 - Dev: Change clang-format from v14 to v16. (#4929)
 - Dev: Fixed UTF16 encoding of `modes` file for the installer. (#4791)
 - Dev: Temporarily disable High DPI scaling on Qt6 builds on Windows. (#4767)