UI: Improve/refactor autoconfig/settings service UI

Makes it so that services can have custom handling on a per-service
basis.  The bottom part of the service pane is now a stacked widget
which can now be customized for different types of services
(particularly OAuth services).

UI/CMakeLists.txt

@@ -134,6 +134,7 @@ set(obs_SOURCES
 	window-basic-auto-config.cpp
 	window-basic-main-outputs.cpp
 	window-basic-source-select.cpp
+	window-basic-settings-stream.cpp
 	window-basic-auto-config-test.cpp
 	window-basic-main-scene-collections.cpp
 	window-basic-main-transitions.cpp