Read the `manifest_path` file and deserializes it using the toml Deserializer. Returns a Result containing `ManifestAndUnsedKeys` which contains `CargoManifest` and a `BTreeSet ` containing the unused keys from the parsed file. # Errors Will return Err if the file (manifest_path) couldn't be read or if deserialize to `CargoManifest` fails.
(manifest_path: &PathBuf)
source not stored for this graph (policy: none)