Use artifact inventory

[runesoerensen]

This PR introduces support for the artifact inventory code shared with the Go buildpack, and updates the GitHub actions for node.js to write a corresponding inventory.toml file in the new format (which includes the sha256 checksum that is used to verify the download, as well as the upstream URL rather than our own S3 mirrored artifact store).

A few notes:

• The shared inventory code is being pulled directly from the Go buildpack. This will be moved to libherokubuildpack at some point.
• The inventory file includes arm64 and amd64 linux artifacts and are resolved based on the current host OS and arch.
• darwin artifacts and the staging channel releases are no longer included in the inventory.
• As the classic nodejs buildpack uses the current implementation for inventory updates, this PR does not update or remove any of the shared code.
• When/if the classic node.js buildpack if migrated to use the new inventory utilities we can remove the node specific code from this repository.

We may also want to consider migrating NPM and Yarn over to the new format at some point (so we can avoid mirroring, and simplify our codebase), but that's probably out of scope for the time being.

[runesoerensen]

The PR is ready to be merged, but I'll hold off doing that until we hear back from the SA team