Use the assets stream wrapper for translated javascript files

Problem/Motivation

Core added an assets: stream wrapper which allows for aggregates to be stored separate from the public files directory, this is mostly for the case when the public files directory is on s3 or a similar remote storage.

#3486412: Very slow Drupal to load translated nodes/many internal redirects to translated pages/ late server response time 15s due to Drupal translation logic. suggests (but does not yet confirm) that serving JavaScript translations from s3 might also be a problem.

Steps to reproduce

Proposed resolution

I think we can just change public: to assets: in the relevant spots, add a change record, and everything will work.

Remaining tasks

User interface changes

Introduced terminology

API changes

Data model changes

Release notes snippet