Simplify hierarchical traversal

## Background
Currently, the hierarchical records generator uses a lot of auxiliary arrays, maps, etc. Maybe if the parser could specify child segments for segment redefines instead of setting parent segment for child segment redefines the traversal could be simplified.

## Feature
Investigate if hierarchical traversal can be simplified.

## Additional context
* Consider using visitor pattern for both nested and hierarchical traversals so that the traversal algorithms can be reused.
* If this could be achieved the traversal algorithms can be moved from `spark-cobol` to `cobol-parser`.