Move audio capabilities out of the renderer classes

Since the removal of libsoundio, all renderers support arbitrary audio duration, so we can avoid having to start an audio session just to query capabilities.

app/streaming/audio/renderers/renderer.h

@@ -15,8 +15,6 @@ public:
     // Return false if an unrecoverable error has occurred and the renderer must be reinitialized
     virtual bool submitAudio(int bytesWritten) = 0;
 
-    virtual int getCapabilities() = 0;
-
     virtual void remapChannels(POPUS_MULTISTREAM_CONFIGURATION) {
         // Use default channel mapping:
         // 0 - Front Left