We need this for a little little longer :(

This reverts commit 1de8383ad9fdfc8f552117e5d109bdfa7005634b.

This removes libnm-glib, libnm-glib-vpn, and libnm-util for good.
The it has been replaced with libnm since NetworkManager 1.0, disabled
by default since 1.12 and no up-to-date distributions ship it for years
now.

Removing the libraries allows us to:

* Remove the horrible hacks that were in place to deal with accidental use
  of both the new and old library in a single process.
* Relief the translators of maintenance burden of similar yet different
  strings.
* Get rid of known bad code without chances of ever getting fixed
  (libnm-glib/nm-object.c and libnm-glib/nm-object-cache.c)
* Generally lower the footprint of the releases and our workspace

If there are some really really legacy users; they can just build
libnm-glib and friends from the NetworkManager-1.16 distribution. The
D-Bus API is stable and old libnm-glib will keep working forever.

https://github.com/NetworkManager/NetworkManager/pull/308

For now only add the core settings, no peers' data.

To support peers and the allowed-ips of the peers is more complicated
and will be done later. It's more complicated because these are nested
lists (allowed-ips) inside a list (peers). That is quite unusual and to
conveniently support that in D-Bus API, in keyfile format, in libnm,
and nmcli, is a effort.
Also, it's further complicated by the fact that each peer has a secret (the
preshared-key). Thus we probably need secret flags for each peer, which
is a novelty as well (until now we require a fixed set of secrets per
profile that is well known).

After renaming the files, also rename all the content
to follow the "Wi-Fi P2P" naming scheme.

We named the types inconsistently:

  - "p2p-wireless" ("libnm-core/nm-setting-p2p-wireless.h")

  - "p2p" ("libnm/nm-p2p-peer.h")

  - "p2p-wifi" ("src/devices/wifi/nm-device-p2p-wifi.h")

It seems to me, "libnm/nm-p2p-peer.h" should be qualified with a "Wi-Fi"
specific name. It's not just peer-to-peer, it's Wi-Fi P2P.
Yes, there is an inconsistency now, because there is already
"libnm/nm-access-point.h".

It seems to me (from looking at the internet), that the name "Wi-Fi P2P"
is more common than "P2P Wi-Fi" -- although both are used. There is also
the name "Wi-Fi Direct". But it's not clear which name should be
preferred here, so stick to "Wi-Fi P2P".

In this first commit only rename the files. The following commit will
rename the content.

This adds the introspection data and P2P peer handling to libnm. To be
usable the P2P device handling is also needed.

This only adds the new device type and simple peer list handling.

The support is rather basic and only allows connecting to a specific
peer. However, this is actually already enough for many usecases.

Add missing trailing commas that avoids getting noise when another
file/parameter is added and eases reviewing changes[0].

[0] https://gitlab.gnome.org/GNOME/dconf/merge_requests/11#note_291585