Use separate metadata keys for the current effective default nodes
(default.*), and user-configured ones (default.configured.*).
default-nodes saves and restores the configured ones, and policy-node
keeps the effective ones up to date.
For pipewire users, the effective default values should be considered
read-only, as changing them will not have an effect. To avoid
confusion, policy-nodes will reset their values back immediately if they
are changed.
Save settings as jason and use a small json compatible tokenizer to
load settings instead of our own less flexible format.
Save settings with a prefix and filter out entries without prefix
Listen for changes in restore.stream metadata and update properties.
