packaging: split vgpu perception into separate libvgpu-perception0 + -dev packages

- the vmsig package no longer ships the gpu lib; it is a Sensor lib for the control, not the daemon
- vgpu-perception gets SOVERSION; runtime (libvgpu-perception0) and dev (-dev) packages, like the vmie split
- per-component install + a 3-package make deb; fix a stale comment (the windows producer is in-tree)

packaging/deb/vgpu0/control.in

@@ -0,0 +1,12 @@
+Package: libvgpu-perception0
+Version: @VERSION@
+Section: libs
+Priority: optional
+Architecture: amd64
+Depends: @DEPENDS@
+Maintainer: @MAINTAINER@
+Description: Host-side vgpu perception library
+ Reads the in-guest vgpu shared region (frames, cursor, geometry) from the host over a
+ read-only guest-RAM handle and exposes a perception API. A Sensor-layer library consumed
+ by a control/shell, independent of the signaling daemon. This package ships the runtime
+ shared object (libvgpu-perception.so.0).

packaging/deb/vgpu0/postinst

@@ -0,0 +1,10 @@
+#!/bin/sh
+set -e
+case "$1" in
+configure)
+    ldconfig || true
+    ;;
+abort-upgrade|abort-remove|abort-deconfigure)
+    ;;
+esac
+exit 0