Checkboxes are usually used when multiple choices can be made from
multiple options.
Radio buttons are usually used when only a single choice can be made
from multiple options.
Enum properties that do not have PROP_ENUM_FLAG can only have a single
chosen value, so this patch changes their menu icons from checkboxes to
radio buttons.
Affected UI primarily includes use of UILayout.prop_menu_enum in Python-
defined UI, such as View>Display Size in the Asset Browser and File
Browser, and the menu for changing a Brush's tool in the Brush Specials
menu.
Thomas Barlow