Favicons not loaded on fresh start

I don't know whether favicons loading was ever working reliably. Looks like they don't load unless you have loaded the page as well during a session. Its possible that qtwebengine does not expose them as image://favicon/https://start.duckduckgo.com/favicon.ico (for example) unless you loaded a page with it.

Either some switch will have to be found allowing to access them or we have to store the favicons into separate cache and access from there.

Note that currently only history gets updated with favicons on their load, not bookmarks (see corresponding call in WebView).