state-stream.lua: add restore-identifiers setting

This adds a new "stream.restore-identifiers" setting that allows to reorder or change the properties used as identifiers to restore stream properties.

This setting can also be set in the "stream.rules" to allow changing "restore-identifiers" for matching streams. Rules could as example match streams with the "Music" role and prioritize "" and "" properties over "media.role" without changing the behaviour of other roles like "Notification" which would happen if the global "stream.restore-identifiers" list is changed.

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