Get buildpacks from latest release for fir apps

[eablack]

GUS WI

Description

With fir, buildpack data is now configured via project.toml and the active state of what buildpacks are installed for an app is not stored explicitly in Platform API. For the buildpacks command, we'll now display that state as derived from the oci image from the latest release of an app.

Testing

1. pull down this branch and yarn build
2. ./bin/run buildpacks --app APP where APP is a cedar app
3. see no difference from what is in production
4. ./bin/run buildpacks --app APP where APP is a fir app
5. See that it does not fail, and displays the relevant cnb buildpack(s)

[sbosio]

Great work!