Compute topological order for package automation script

[deciduously]

Currently, the automation script just runs alphabetically, using checkins of packages that were tagged with local paths. We want to instead check in with --local=false before tagging and pushing package directories to ensure cache hits, which requires computing an order that ensures the script only builds packages for which all dependencies are already tagged and pushed.

The implementation will be a Rust CLI tool using the Tangram client and petgraph, which accepts a list of packages and returns the list sorted topologically. The automation script can shell out to this script instead of the current list.sort() implementation of included package names.