Add a new struct spa_param_info that lists the available params on
a node/port and if they are readable/writable/updated. We can use
this to replace and improve the PARAM_List and also to notify
property change and updates.

Update elements and code to deal with this new param stuff. Add
port and node info to most elements and signal changes.

Use async enum_params in -inspect and use the param info to know
which ones to enumerate.

Use the port info to know what parameters to update in the
remote-node.