New categories: both virtual and non virtual

Hello everyone,

with pkg 1.18, it is easier to add new catagories which and reduce the impact
in people as we can query all the categories virtual or not.

Now that this is done, I would like to add the following new categories. Not
that I want to address the current isssue here which is the desktop world on
FreeBSD is not anymore a x11 only world, and the categories do not reflect
that reality anymore.

Virtual:
- wayland

Non Virtual:
- ui-toolkits (all UI toolkits should be moved here)
- desktop (all wayland compositors, all apps desktop oriented which does not
  fit in any other catagories).
- desktop-libs (all libraries not ui-toolkit which are necessary for the
  desktops)
- fonts (fonts and related libraries)


For all the x11 related ports which will be moved there will they will keep
a x11* virtual category to it is still queryable that way if it makes sence

For example if we move libinput from x11/libinput to desktop/libinput then the
CATEGORIES= x11 will become CATEGORIES= desktop-libs x11

meaning:
pkg info desktop-libs/libinput will match the same package as x11/libinput

Best regards,
Bapt