Provides access to the icons associated with web sites.
WebKit will automatically look for available icons in <link> elements on opened pages as well as an existing favicon.ico and load
the images found into a memory cache if possible. That cache is frozen to an on-disk database for persistence.
If WebKitSettings:enable-private-browsing is true, new icons won't be added to the on-disk
database and no existing icons will be deleted from it. Nevertheless, WebKit will still store them in the in-memory cache during the
current execution.