Feature request: package ID specification

[LukeMathWalker]

It is possible to access the PackageId attached to each crate in a workspace via guppy, but I can't see any functionality to generated a valid package ID specification starting from that PackageId (or, more likely, its PackageMetadata.

This would be quite convenient when having to issue other cargo commands!

(Moving this issue over from the other repo 👍🏻 )