Fixes#2358
This property can be used to identify the full path to the node that
logged a given message. If the node is inside a subflow (and maybe
nested many levels deep), this path can be used to help find the
node, rather than just the top-level subflow instance node.
A side-effect of this change is the Debug sidebar is now able to
show the message tools for a message coming from a deeply nested
subflow