Add a new PortConfig parameter to configure ports of elements that
are marked with the SPA_NODE_FLAG_*_PORT_CONFIG. This is used to
configure the operation of the audioconver/audioadapter nodes and
how it should convert the internal format. We want to use the
Profile parameter only for cases where there is an enumeration of
values, like with device configuration.
Add unit tests for audioconvert and adapter to check if they handle
PortConfig correctly.
Make the media session use the PortConfig to dynamically configure
the device nodes.
Remove audio-dsp, it is not used anymore and can/should be implemented
with a simple audioconvert spa node now and some PortConfig.
Remove the CAN_USE_BUFFERS flag, it is redundant. We can know this
because of the IO params and buffer params.
Add flags to the port_use_buffer call. We also want this call to
replace port_alloc_buffer. Together with a new result event we can
ask the node to (a)synchronously fill up the buffer data for us. This
is part of a plan to let remote nodes provide buffer data.
