modules: switch protocol-native to the new logging system

This is more complicated than a normal module because we have two
logging topics: mod.protocol-native and conn.protocol-native for wire
messages. Because the latter use spa_debug (through spa_debug_pod) we
need to #define our way around so those too use the right topics.

Note that this removes the previous "connection" category, it is now
"conn.protocol-native" instead.