The WebRTC echo canceler can support different rates and channels for
the record, out and playback streams.
Add a new method to pass this config to the echo-canceler.
Make it possible for a aec-plugin to provide props/params
through module-echo-cancel and make it possible for a
aec-plugin to listen and react to these props/params getting updated.
Add method enum_props() that is used under setup_streams() to
get props from aec_plugin.
Add get_params() and set_params() for updating and getting
aec-plugin params under the input/output_param_changed calls
and getting params under setup_streams().
Add methods activate() that is called before first call to run() when
stream starts and deactivate() that is called after last call to run()
when stream stops. This makes it possible for aec-plugins to reset their
state between streams.
Place the methods on the interface so that we can call them.
Rename create to init because that is what it does.
Add support for listener and events so that we can signal property
changes later.
Move all backends to dynamic libaries loaded with spa_plugin_loader so
new backends not needs changes in pipewire or pipewire dependency to
external code
Change-Id: I702ce047598d0c318d6dc6ac8248062a5c12f643
