v2 build system is missing locales

V2 build system is missing locales (`apt install locales`), resulting in any build that contains calls to [`setlocale`](https://man7.org/linux/man-pages/man3/setlocale.3.html) defunct (e.g. [Pelican](https://getpelican.com/)-based build with its setting `LOCALE = ['en_US.UTF-8']` or its `DATE_FORMATS`). Only locale `"C"` works, but this then, among other issues, limits rendering datetimes to American standards, which are far from universal. 😅

Similarly reported in this blog post: https://herrickfang.com/2023/11/26/cloudflare-workers/

The issue obviously cannot be worked around with `UNSTABLE_PRE_BUILD=` (due to disabled sudo) nor asdf.

This was not an issue in v1.

Start by locating the v2 build-image definition and its package-installation setup; the issue identifies `apt install locales` and failures involving `setlocale`, including Pelican's `en_US.UTF-8` setting. Done means v2 builds support non-C locales such as `en_US.UTF-8` without requiring sudo, an unstable pre-build command, or asdf.

Written by the indexing model from the issue text.