SDL: Select audio device (#2403)

* Initial Commit

Added Device logic to Sinks
Started on UI for selecting devices

Removed redundant import

* Audio Core: Complete Device Switching

Complete the device switching implementation by allowing the output
device to be loaded, changed and saved through the configurations menu.

Worked with the Sink abstraction and tuned the "Device Selection"
configuration so that the Device List is automatically populated when
the Sink is changed.
This hopefully addresses the concerns and recommendations mentioned in
the comments of the PR.

* Clean original implementation.

* Refactor GetSinkDetails

src/citra/config.cpp

@@ -82,6 +82,7 @@ void Config::ReadValues() {
     Settings::values.sink_id = sdl2_config->Get("Audio", "output_engine", "auto");
     Settings::values.enable_audio_stretching =
         sdl2_config->GetBoolean("Audio", "enable_audio_stretching", true);
+    Settings::values.audio_device_id = sdl2_config->Get("Audio", "output_device", "auto");
 
     // Data Storage
     Settings::values.use_virtual_sd =

src/citra/default_ini.h

@@ -91,6 +91,10 @@ output_engine =
 # 0: No, 1 (default): Yes
 enable_audio_stretching =
 
+# Which audio device to use.
+# auto (default): Auto-select
+output_device =
+
 [Data Storage]
 # Whether to create a virtual SD card.
 # 1 (default): Yes, 0: No