FR: Support partial installation

Currently, apt rules assume that installations always happen from scratch, meaning that the underlying system does not have any apt packages installed on it.

This is true if you are building a base image with rules_distroless, but often users use a base image that has some apt packages already installed, making rules_distroless suboptimal at best.

I am proposing a feature where the manifest can instruct our resolver to continue where base image left off reusing package information at /var/lib/dpkg/status within the base image or expect users to list all the packages that already present.

Option 1

In terms of DX, this api is unpleasant, but comes with great flexibility.

manifest.yaml

exclude:
    - base-files
    - base-passwd
    - bash

Option 2

This option autimatically derives the package information by walking through layers. While easier to use since users already have a base image passed to oci_image and can easily add it to their apt.install calls, is less flexible.

apt.install(
 
   base = "@base_image_from_oci_pull"
)