Fixes #1

This is a situation that always happens on startup, so let's not
spam with warnings

signal emission apparently does not work in _finalize()

Fixes some critical warnings from remote-endpoint.c because disconnection
from the destroyed endpoints did not happen

Proxy global id

See merge request gkiagia/wireplumber!11

spa audioconvert (the backend of audio-dsp) does not adevertise
property changes, therefore subscribe_params() is useless.
In order to get the real value from the node we need to call
enum_params() manually.

https://github.com/PipeWire/pipewire/issues/157

This provides high level volume controls for the AGL audiomixer
binding and the applications using it.

We now have always a "selected" endpoint for each direction (source, sink)
that is picked as the first available endpoint at startup,
and it changes automatically if the currently selected endpoint is removed

This avoids the theoretical crash that would happen if you change
the control value on an endpoint whose client-endpoint proxy has
already been destroyed

This avoids being able to find the same object on the globals list
from code that is connected to the signal.

Unregister endpoint

See merge request gkiagia/wireplumber!10

modules: fix proxy ref-count

See merge request gkiagia/wireplumber!9

avoids criticals and crashes when the core is destroyed earlier

+ add a method to retrieve the core
+ change the register function to not require the core as a parameter

Use proxy api in module-pipewire and simple-endpoint

See merge request gkiagia/wireplumber!8

This is a cleaner way to interface with the remote pipewire daemon.
The WpRemote base class can be subclassed also for interfacing
with other daemons (hardware-specific managers, etc)

Proxy API

See merge request gkiagia/wireplumber!7

This can be used by code that depends on policy to re-evaluate
choices they have made in the past that could now change based
on the new policy.

We need to delay the registration of the simple endpoint because
it needs to get some information from the "info" callback of pipewire
before we can use it in a link.

Only one endpoint of a certain media class can be selected at a time