WpDevice, WpSpaDevice, WpNode, WpImplNode, WpObject and object features

port module-monitor to follow the changes

A new desktop profile without endpoints will be added.
The goal is to be compatible with media-session in the short term

Use the unused 'K' format letter in the varargs builder & parser methods

* Use a more complete API to introspect SPA types
* Avoid the need for the Tables enumeration; the tables
  are now registered with a string
* Avoid the need for initialization, work directly on spa_types
  and other static data
* Allow working with Object pods that are not Params;
  the PARAMS table was previously hardcoded in the pod implementation
* Add a different dynamic type registration system, closer to
  how spa type works. The only regression is that we can no longer
  register additional custom object fields (custom SPA_PROP_* for example),
  but this feature can be re-added later

Still missing a way to get the default endpoints, but this
is going to change and use the metadata API

... and make WpIterator Lua-friendly so that it can be used
with the generic for loop

Fixes #22

Fixes #20

Use the same set of warning flags that pipewire uses

See #20

a module that allows loading and executing Lua
scripts from a configured directory

... and improve its output

This patch allows configuring an "extension" string that filters
files not only by extension, but also by a subdirectory of the
standard configuration path(s).

The "extension" can now have the following format:
  "subdirectory/path/extension"
which is split on the last '/' and looks for files that end with
".extension" in "WIREPLUMBER_CONFIG_DIR/subdirectory/path/"

If no subdirectory is specified, the code behaves just like it did
before.

All loaded scripts can now be run in a protected environment
so that they cannot do any harm to the host or to each other