Upgrade Alpine version in base images

3.19 seems to be the latest one available:

https://alpinelinux.org/releases/

From the [upgrade notes](https://www.alpinelinux.org/posts/Alpine-3.19.0-released.html), it's worth checking if this would affect us:

> Python’s package directory is now [marked](https://gitlab.alpinelinux.org/alpine/infra/aports/-/commit/6c2a300f6787544f3194e7f6cc19058baf9b7419) as [externally managed](https://packaging.python.org/en/latest/specifications/externally-managed-environments/), which means that pip can no longer install to system directory which is managed by apk. Users may use [pipx](https://pipx.pypa.io/stable/) instead