Remove font height restriction from Button

[KoBeWi]

Possible fix #35005
The button height is determined by the text buffer, so additinally using font height is not necessary.

[Calinou]

How does this behave when the button is within a Container with no custom minimum size set?

[KoBeWi]

It shrinks to the stylebox size (the same as show in the GIF). This change only affects buttons without text, so it doesn't break anything in majority of the cases.

[Geometror]

Seems reasonable to me. However, we have to keep in mind that this has an effect on the editor UI (vertical shrinking), which might require some adjustments. For example, the OptionButton arrow isn't centered anymore in some cases and a few controls which had the same height before now have different heights. Both observable here:
Before:

After:

GIF before/after of whole editor:

[fire-forge]

Not a bad idea. Could be useful for icon-only buttons where the font height is taller than the icon.

[KoBeWi]

@Geometror OptionButton will be handled by #59303, other buttons don't really have this problem.

[Geometror]

I only checked the most common areas, but altough some elements shrink in height (as seen in the GIF) they still look good. There is only one nitpick, the plus icon of the "Add new scene" button in the central tab bar moves up 1 px, making it look a bit off-centered :)

[Geometror]

Just noticed that some Color inspector properties are squished heavily:
Before->after:

[KoBeWi]

Maybe bruvzg's suggestion makes sense actually...

EDIT:
Ok changed it so that the height is ignored only when the text is empty. This should fix all shrinking issues.

[YuriSizov]

Just noticed that some Color inspector properties are squished heavily: Before->after:

This is actually a good thing and the fix working as intended, IMO. ColorPickerButton shouldn't depend on the height of the font, and we should just adjust its theme properties to give it more initial height to match the UI.

[Geometror]

The shrinking is still present (at least in color theme overrides section) but I agree with what @YuriSizov said, this could be fixed by adjusting the ColorPickerButton style/minsize (in this or a subsequent PR).

[akien-mga]

So from the above discussion it sounds like there are still pending issues to solve before merging this?

[KoBeWi]

There are some tweaks that need to be done to buttons that don't have any text, but it could be left for a subsequent PR. Not sure what's preferred; it's not directly related to the changes here.

[Geometror]

I think this can be merged. The tweaks needed for the editor UI can be done separately.

[akien-mga]

Thanks!