Merge hierarchy package into transform package

[yohamta]

Since we typically use the hierarchy and transform packages together, we plan to merge them into a single package. Additionally, utility functions in the hierarchy package should be made private since they are only used internally.

Change overview

• Renamed functions in hierarchy package with the hierarchy prefix
• Moved files from hierarchy package into transform package
• Made internal hierarchy manipulation functions private

[yohamta]

I've made these changes quickly. Could you please review them when you have a chance? @m110

[m110]

Thank you @yohamta! Will try it out 🤝

[yohamta]

Cool, thank you for taking a look!