[Core] Better tabbar size hint calculation.
[LMP] Refactored artists buttons to StdArtistActions for #1437.
[LMP] SysIconProvider -> ThemeImageProvider in SimilarView.
[LMP] SysIconProvider -> ThemeImageProvider in HypesWidget.
[LMP] SysIconProvider -> ThemeImageProvider in ReleasesWidget.
[LMP] Removed SysIconsProvider.

Util::ThemeImageProvider is a way to go.
[LMP] Provide sysIcons for BioView for #1437.
[LMP] Proper icon for audio preview.
[LMP] Refactored artist actions handling for #1437.
[LMP] Add std artist actions to bio view.

This finally closes #1437.