with ISOLATE_ENV, it isolates the global environment between scripts
just like it did before; without it, it uses a common environment

with MINIMAL_STD, it restricts even further the available library
functions; useful for configuration files that don't need to do
actual scripting, just to define some tables

The component loader is a more generic and extensible mechanism
of loading components; modules are one type of component...
The idea is to make scripts and config files also be components,
loaded by plugins that inherit WpComponentLoader

* use the activate/deactivate system from WpObject,
  which allows async activation and error reporting
* drop 'module' property, use 'core' from WpObject

This is useful for monitors to destroy the associated device reservation
object. And it may be useful for other things in the future...

Similar to wp_si_factory_find()

Depends on DeviceEvent type-info, available on pipewire master as of today

port module-monitor to follow the changes

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

Fixes #20

... 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

This is no longer useful, we are going to use WpSpaPod directly
in combination with the param caching for WpPwObjectMixin

Now the WpPipewireObject interface is directly implemented by the mixin
and there is another interface that users of the mixin must implement
in order for the mixin to work proprely.

A lot of manual stuff that proxy classes had to do before are now
in the mixin. Also most of the data that would normally reside in Private
structures is now in the mixin data structure (stored as qdata on the object).
This is achieving the best amount of code reuse so far.

For impl objects (WpImpl*) there are also default implementations of the
standard pipewire object methods and the INFO & PARAM_* features are
more coherently enabled during the whole lifetime of these objects.

Similar to how pipewire interfaces are versioned.
Keeps the struct extensible without breaking ABI.