Test all renderers before use

Every renderer except SDL had opted-in for testing due to various
quirks discovered over the years, so just do away with this option
and test all renderers.

app/streaming/video/ffmpeg-renderers/plvk.h

@@ -26,7 +26,6 @@ public:
     virtual int getDecoderColorspace() override;
     virtual int getDecoderColorRange() override;
     virtual int getDecoderCapabilities() override;
-    virtual bool needsTestFrame() override;
     virtual bool isPixelFormatSupported(int videoFormat, enum AVPixelFormat pixelFormat) override;
     virtual AVPixelFormat getPreferredPixelFormat(int videoFormat) override;