The event contains the names (NB: not the package id's) of packages which were detected in the current cargo workspace.

Possibly must be sent optionally in the future, because we should also support non cargo workspaces.

This works around some issues like:
- cargo metadata only works for cargo projects, which is fine for most  of  our defaults, but we only hard require rustup right now for compatibility check commands like find and verify
- an unwrap panic from within cargo metadata if it was given an invalid path

Yet, the current choice is a pragmatic one and may not account for all cases or handle all errors.