We have a new, improved string type coming up in AK (OOM aware, no null
state), and while it's going to use UTF-8, the name UTF8String is a
mouthful - so let's free up the String name by renaming the existing
class.
Making the old one have an annoying name will hopefully also help with
quick adoption :^)
This was intentionally enabled with WindowModes as a new Taskbar
convenience, but on second thought, it doesn't add up visually.
Taskbar buttons show blockers' context menus when available,
which is a bit confusing when the window isn't visible. The
modeless window's disabled context menu options and inactive title
bar also contradict the button. So, this patch reenables the
restriction for now. Blocking modals you don't want to answer to
immediately can still be tucked away on another workspace.
