RFC: delegates: Enable tooltips by default when text is truncated

This is behavior that used to be the default with BasicListItem and which was ported over to the new Kirigami content items. However, since that limits it to the content item, the tooltip will not display when the content item is too small. Additionally, this means tooltips only show up when using these content items.

Instead, we can enable the tooltip on the delegates directly, which means the entire delegate becomes the trigger surface. Since these are just setting defaults for the tooltip properties, it means they can be easily overridden when tooltips should be disabled or when it should display something different.