3.4 editor theme is missing icons for disabled checked items

[KoBeWi]

Godot version

3.4

System information

W10

Issue description

As originally mentioned in #37755 (comment), the editor theme in Godot 3.4 is missing icons for disabled checked and unchecked (radio) checkboxes. On master they were added in #51722

The icons might be worth backporting probably.

Steps to reproduce

No response

Minimal reproduction project

No response

[Deozaan]

the editor theme in Godot 3.4 is missing icons for disabled checked and unchecked (radio) checkboxes

This seemed ambiguous to me, so I just wanted to clarify that all of the disabled checkbox icons are missing from the theme in 3.4. Not just the radio checkbox icons.

[timothyqiu]

Closed by #59857