This fixes some log spam.

This way the embedded json metadata of the C++ plugins will be used instead.

By moving the main.qml file to a "ui"-subfolder we don't need to
configure the paths for the mainscript, but can just use the defaults.

To test this change, all the KCMs packages in "PREFIX/share/kpackage/kcms/"
should be removed. Otherwise we might have some leftovers lying around.

looks nicer!

this twiddles with the UI a lot, a change I didn't want to make when I
rewrote the modeling tech for 5.18 to unbreak the kcm.

on the backend side this mostly just changes the previous column system
to an actual role system for the model as that is nicer to use from qml.
also more useful values are now being modelled in addition to the raw
backend data. notably a working shareurl can be constructed so long as
we can resolve a FQDN from avahi.

on the GUI side the entire kcm is now written in qtquick and requires
kdeclarative 5.74 due to its use of AbstractKCM

the two views are still on the same page but use more appealing
delegates now instead of plain tables. furthermore the delegates have
been made interactable where useful (shares can be edited, fully
qualified urls clicked, mounts can be clicked to open dolphin)