Add port direction again

simplify port numbering again by using 0->max_ports for bot input ports
and output ports. This means we need to tall what direction the port is.
Add port_info serialize functions
Copy metadata and data when we are not sharing buffers.
Make pinossink work again.

spa/lib/meson.build

@@ -3,6 +3,7 @@ spalib_sources = ['audio-raw.c',
                   'control.c',
                   'debug.c',
                   'format.c',
+                  'port.c',
                   'props.c',
                   'ringbuffer.c',
                   'video-raw.c']