monitors/libcamera: load node locally

At the moment the libcamera monitor and "Device" objects are loaded in the
wireplumber process, but the "Node" objects are loaded in the pipewire daemon.
Due to that, both processes have their own separate `libcamera::CameraManager`
objects. These operate independently.

As a consequence of the above, there is an inherent race condition: when a
new camera appears and the wireplumber process detects it and instructs the
pipewire process to create a "Node" for it, at that point, the camera might
not exist in the `CameraManager` of the "pipewire" process.

This can happen during the initial enumeration as well as hotplug. So load
the nodes locally in the wireplumber process so that all libcamera objects
use the same `CameraManager`, thus eliminating the race condition.

src/config/wireplumber.conf

@@ -470,6 +470,9 @@ wireplumber.components = [
   {
     name = monitors/libcamera/create-node.lua, type = script/lua
     provides = hooks.monitor.libcamera-create-node
+    requires = [ support.export-core,
+                 pw.client-node,
+                 pw.node-factory.spa ]
   }
   {
     name = monitors/libcamera/enumerate-device.lua, type = script/lua

src/scripts/monitors/libcamera/create-node.lua

@@ -34,7 +34,7 @@ SimpleEventHook {
       return
     end
     -- create the node
-    local node = Node ("spa-node-factory", properties)
+    local node = LocalNode ("spa-node-factory", properties)
     node:activate (Feature.Proxy.BOUND)
     parent:store_managed_object (id, node)
   end