Use CI cache to speed up `npm ci`

[achrinza]

This issue is to track using of CI caches to speed up CI workflows.

To enable caching for NPM-based projects:

• Add the cache: npm input to instances of the actions/setup-node Github Action:

  using: actions/setup-node@v4.0.0
  with:
    cache: npm
  

• Add --prefer-offline to instances of npm ci
  This will stop NPM from performing "staleness" checks, without the "hard failure" of --offline.

Restrictions

The storage of cache is 10 GB per-repository, with a maximum "no access" duration of 7 days. If any of these limits are hit, they will be automatically evicted. Hence, there should not be much additional maintenance oerhead for us.