Fix node lineage in JexlNodeFactory.createNodeTreeFromFieldsToValues

[apmoriarty]

This is a second cut of https://github.com/NationalSecurityAgency/datawave/pull/1273 after the changes to refactor the parallel index expansion.

Change summary

• instead of building out nodes in-place, children are built first and the parent node is build last (simplifies logic)
• more instances of copying a node (preserves node lineage)
• added tests for JexlNodeFactory and UnfieldedIndexExpansionVisitor

[FineAndDandy]

This looks consistent, but hard to tell if it's 100% correct.