v2023.02.04

Upstream changes

• Merge pull request 'Attempt calculating custom favicon avg color, only try calculating once' (#99) from wn/tt-rss:feature/custom-favicon-detect-color into master
• Minor tweak to favicon avg color debug log message.
• Don't set 'favicon_avg_color' on feed obj unless it's valid.
• Fix logging favicon-related bools in 'RSSUtils::update_rss_feed()'.
• Persist failure to detect favicon average color.
• Ensure custom favicon color detection happens.