Utils - memoize, calculateTextDimensions (and friends), assignWithDepth, etc

[cmmoran]

📑 Summary

Added a few QoL functions to utils. No new modules introduced.

• memoize: simple caching for computationally intensive functions. This comes in handy for things like calculating text dimensions (especially the way we do it with drawing to an svg canvas and then removing the element - this gets quite expensive quite quickly)
• assignWithDepth - this is essentially a franken-merge of what we were doing with config.js and Object.assign. The goal / purpose of this function is to provide a sane mechanism for merging arbitrarily deep objects
• calculateTextDimensions, calculateTextWidth, calculateTextHeight - for measuring text
• random - similar to generateId except it generates random values based on the crypto-random-string package (already added to this project)

📏 Design Decisions

Added a fair number of unit tests to utils.spec.js.