this is a factored implementation usable by all non-web frontends. Sources and Sinks can
be configured easily to use tests source or local webcam/microphone, autosinks or a
`appsink` that the frontend will use.
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- `run_from_thread` can be used to run a method from a thread.
- `maybe_async` can be used to run a method if we are not sure if it's async or not.
- `install_glib_asyncio_iteration` run the GLib loop from asyncio one's.
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