* core no longer exposes create_remote/local_object
* node, device & link have constructor methods
  to enable the create_remote_object functionality
* added WpImplNode to wrap pw_impl_node and allow creating
  "local" node instances
* added WpSpaDevice to wrap spa_device and allow creating
  "local" device instances
* exporting objects in all cases now happens by requesting
  FEATURE_BOUND from the proxy, eliminating the need for WpExported
* replaced WpMonitor by new, simpler code directly in module-monitor
* the proxy type lookup table in WpProxy is gone, we now
  use a field on the class structure of every WpProxy subclass
  and iterate through all the class structures instead; this is
  more flexible and extensible

The alsa.pcm devices currently use "device.api" = "alsa:pcm"
but then the node overrides this later to just "alsa", which
is confusing. For now, let's match "alsa:pcm" in the monitor,
even though this does not appear on the node later.

This commit fixes device preferences in wireplumber.conf,
which were broken because the alsa endpoint names were empty
of info about the alsa device

This is a generic WpMonitor loader that sets up the WpMonitor
properties from the module arguments and applies some well-known
properties to the device & node objects