This removes the ability to add specific tooltips for icons in text. It was introduced in rP8494 for the Civilisation overview.
It's still only used there.
This removes a fair amount of code, and the 'privateness' of the setting was always a horrible hack.
Obviously, the drawback is won't be able to embed tooltips on icons in text. This could be useful for a 'civilopedia' style text entry, but realistically it would be useful to have more functionality then, and icons seem like they'd mostly lead to a lot of duplication. It's probably better to have CText create _proper_ objects in their place, even if that will require special handling too.
On the Civ Overview page, this replaces the inlined text with repeated sub-elements (as I suspect would have been done from the start if we'd had these then). It seems cleaner, and the tooltip is now on the whole text instead of just the 'i' which see fine for me.