Make IndexTrie take nodes (#8649)

Make IndexTrie take nodes (#8649)

This makes the class easier to use and allows for a usage where the null node is interpreted as specifying all nodes.

This is in preparation for using this class for testing whether an instantiation from any instantiation strategy is currently feasible based on learning in the style of fail masks from Janota et al FMCAD 2021.

Also, this class should be renamed to something more appropriate, since it no longer takes indices.

FYI @MikolasJanota