Fixes#18563 by adding the etag header to the optimized image response.
This does _not_ change the expireAt (TTL) for cached files on the server, which still uses the max-age of the upstream response.
The new file format on disk for cached image files is the following:
```
.next/cache/images/<HASHED_QUERYSTRING>/<EXPIREAT>.<ETAG>.<EXT>
```
This upgrades to ncc@0.25.0 and fixes the previous bugs including:
* ncc not referenced correctly in build
* Babel type errors
* node-fetch, etag, chalk and raw-body dependencies not building with ncc - these have been "un-ncc'd" for now. As they are relatively small dependencies, this doesn't seem too much of an issue and we can follow up in the tracking ncc issue at https://github.com/vercel/ncc/issues/612.
* `yarn dev` issues
Took a lot of bisecting, but the overall diff isn't too bad here in the end.
