Cargo lockfile V2 not supported

[cberner]

Cargo switched to a new lockfile format by default (rust-lang/cargo#7579). It seems like this format isn't supported. Running lichking on a project which uses the new format results in the following error message:

error: failed to parse lock file at: /home/cberner/Code/fleetfs/Cargo.lock

Caused by:
  invalid serialized PackageId for key `package.dependencies`