Add an icon to show that settings have tooltips

[Mm2PL]

Fixes #6833. This explores the Factorio-esque icon idea.

Icon is made by me

Co-authored-by: -
Tested-by: -
Reported-by: Mm2PL
Reviewed-by: -
Parent-pr: -

[Nerixyz]

Some comments:

• Having the icon in the top left corner looks weird - I'd prefer if this was similar to your screenshot in Settings should have a tooltip indicator #6833 of Factorio.
• I'd prefer the icon to be an i (similar to Factorio), though we usually use the outlined icons.
• Some settings have a colon after the name. With the tooltip indicator, this looks off.
• The tooltip on the indicator should have a smaller delay (maybe even no delay at all?).
• On high DPI screens, the icon looks blurry.

[Mm2PL]

- Having the icon in the top left corner looks weird - I'd prefer if this was similar to your screenshot in #6833 of Factorio.

I centered it

- I'd prefer the icon to be an `i` (similar to Factorio), though we usually use the outlined icons.

I'll make an ⓘ version soon™.

- Some settings have a colon after the name. With the tooltip indicator, this looks off.

It does. Putting the icon after the action element (eg combo box) looks even more wrong to me

- The tooltip on the indicator should have a smaller delay (maybe even no delay at all?).

This is a Qt limitation I believe. Unless we want to make our own tooltip machinery. We cannot change that, I'll look into it but if it turns out too complex I will not be doing it in this PR.

- On high DPI screens, the icon looks blurry.

That's apparently because of the 'width' and 'height' attributes on the root elem. Hopefully using a QSvgWidget will help with that.