Webpacker migration

[pgwillia]

Webpacker is deprecated/end of life now and has been a source of many CVEs for this project. We will migrate our JS assets to Esbuild (via jsbundling) and css/image assets back to sprockets (+ cssbundling).

This is more aligned with the recommended approach from Rails. (e.g if you generate a new Rails 7 application most likely you would use esbuild or importmaps)

Similar to ualbertalib/jupiter#3320

[murny]

Code for this is all done and has been merged. Will close this issue once it's deployed out to production.