Turn color button into a box
- As a side effect renamed entry_color_button to entry_color_box and remove button specific properties
- To emulate the circular class for buttons, a border-radius of 16px is used. This is a hack and should be improved and a TODO note was added to reflect on this.
By not being a button anymore Fixes: https://gitlab.gnome.org/World/PasswordSafe/-/issues/226