[docker] Build hailtop-slim image with just hailtop

[daniel-goldstein]

This creates another hailgenetics image with just hailtop and its python dependencies installed (no hail query, no java, no gcloud), primarily useful for using the copy tool. In contrast to hailgenetics/hail's 2.89GB on disk, hailgenetics/hailtop-slim is 289MB.

[jigold]

I think you need to rebase again.

[jigold]

Does this need to be incorporated some how into the bootstrapping process?

[daniel-goldstein]

This has diverged significantly and contains parts of some changes to handling hailgenetics images that was handled in separate PRs. Closing in favor of #12446 which is much simpler.