Merge pull request #23943 from vrabaud:avif_tsan

Fix checkSignature not thread safe for AVIF. #23943

A common decoder cannot be shared with checkSignature which is used like a static function (on a static ist of decoders).

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- [x] I agree to contribute to the project under Apache 2 License.
- [x] To the best of my knowledge, the proposed patch is not based on a code under GPL or another license that is incompatible with OpenCV
- [x] The PR is proposed to the proper branch
- [x] There is a reference to the original bug report and related work
- [x] There is accuracy test, performance test and test data in opencv_extra repository, if applicable
      Patch to opencv_extra has the same branch name.
- [x] The feature is well documented and sample code can be built with the project CMake

modules/imgcodecs/src/grfmt_avif.cpp

@@ -148,11 +148,14 @@ AvifDecoder::~AvifDecoder() {
 size_t AvifDecoder::signatureLength() const { return kAvifSignatureSize; }
 
 bool AvifDecoder::checkSignature(const String &signature) const {
-  avifDecoderSetIOMemory(decoder_,
+  avifDecoder *decoder = avifDecoderCreate();
+  if (!decoder) return false;
+  avifDecoderSetIOMemory(decoder,
                          reinterpret_cast<const uint8_t *>(signature.c_str()),
                          signature.size());
-  decoder_->io->sizeHint = 1e9;
-  const avifResult status = avifDecoderParse(decoder_);
+  decoder->io->sizeHint = 1e9;
+  const avifResult status = avifDecoderParse(decoder);
+  avifDecoderDestroy(decoder);
   return (status == AVIF_RESULT_OK || status == AVIF_RESULT_TRUNCATED_DATA);
 }