In recent libheif, application should use
heif_init/heif_deinit calls. Unfortunately, these calls are
not thread-safe in released 1.13.0 version yet (will be in the
future) and HEIFHandler is often created in different threads.
So we have to guard their use with a mutex.
To make the plugins fail to allocate if the image size is greater than QImageReader::allocationLimit() it is necessary to allocate the image with QImageIOHandler::allocateImage().
Note that not all plugins have been changed and some others are not tested in the CI (maybe due to missing libraries).
PS: the following message is printed by QImageIOHandler::allocateImage() if the size is exceeded: "qt.gui.imageio: QImageIOHandler: Rejecting image as it exceeds the current allocation limit of XXX megabytes"
