avif: enable decoding of files with invalid EXIF metadata

When 1st parsing ends with invalid EXIF payload error,
we try 2nd time again while ignoring the EXIF metadata.

Dropped support for legacy 0.x libavif versions,
libavif 1.0.0+ is now required for the AVIF support.

src/imageformats/avif_p.h

@@ -47,6 +47,7 @@ private:
     static QPointF CompatibleChromacity(qreal chrX, qreal chrY);
     bool ensureParsed() const;
     bool ensureOpened() const;
+    bool initDecoder(bool ignore_exif);
     bool ensureDecoder();
     bool decode_one_frame();