main/alpine-base: add ca-certificates-bundle

Considering that default /etc/apk/repositories now uses HTTPS, and the vast majority of websites require HTTPS, it is past time to officially declare ca-certificates-bundle part of the "standard Alpine installation". Users that want the smallest possible installation can uninstall alpine-base and install its components individually, but will be expected to pick up the pieces themselves (e.g. apk repositories).

fixes #5821.