QSGTexture::comparisonKey() return type should not be int

...but rather something like qintptr. In Qt 6 all internal implementations of this function will massage a QRhiTexture pointer into the return value, whereas custom, application-side implementations will likely work with native resource handles, such as VkImage, MTLTexture*, ID3D11Texture2D*, GLuint, etc. (some of which are pointers, some not)