Return a node list of Info FILENAME with parent-children information.
This information is cached in the variable `Info-toc-nodes' with the help
of the function `Info-toc-build'.
Alist of cached parent-children node information in visited Info files.
Each element is (FILE (NODE-NAME PARENT SECTION CHILDREN) ...)
where PARENT is the parent node extracted from the Up pointer,
SECTION is the section name in the Top node where this node is placed,
CHILDREN is a list of child nodes extracted from the node menu.