Finish migration to Turbo.js to remove JS delay

[arkirchner]

A new event was introduced to ensure that asset pipeline JavaScript is loaded before execution of JS features. This causes some delay until JS features are available. Realized issues are that confirmations from UJS are only working after a little while.

https://github.com/openHPI/codeocean/blob/main/app/javascript/turbo-migration.js

TODO:

• Move all JavaScript to Webpack to avoid order dependency issues.
• Remove migration event.