This also brings the advantage that all tools, examples, modules, components
can also be compiled standalone out-of-tree using libpipewire from the system
The motivation is to have both existing and new streams that have been
created without explicit target node, to be directed to the same devices
at all times. To achieve this:
Consider what find_node returns as the "default node".
Consider streams that auto+reconnect and don't have an explicit target,
as following default. In rescan, if the default node has changed,
relink such streams to the new default.
Remove the old code that explicitly moved streams when the default.*
metadata changed, as it implements a similar thing but in a less robust
way (may fail to do what's intended, because the default device
metadata is commonly unset, or the metadata callback comes before
session_create has seen the new nodes).
Enable this feature based on "policy-node.streams-follow-default"
property. Allow setting the property also by loading the
streams-follow-default module. Enable it by default only for the
with-pulseaudio module group.
