Increase h separation of editor's PopupMenu

[KoBeWi]

Before:

After:

(this is scene dock's ⋮ menu)

Closes #81964

[akien-mga]

Looks better, though I notice there seems to be more spacing between the separation line and the left of the icon, than on the right of the label. Can this be tweaked?

[KoBeWi]

Not with a theme constant AFAIK.

[YuriSizov]

Looks better, though I notice there seems to be more spacing between the separation line and the left of the icon, than on the right of the label. Can this be tweaked?

I think this is actually the source of the issue. There is clearly enough space allocated to both the separation and the icon, but the icon itself is not drawn centered to that space. I'm looking into it, but the drawing code is a mess.

Edit: Okay, it's because of the item padding added on both sides. It shifts the icon, but not much else. I'll make a PR.

[YuriSizov]

Done #83517.

[KoBeWi]

Superseded by #83517