Use new checksums in manifest

Summary: This now makes use of the `tarsum` mod to surface both intrinsic and extrinsic checksums as part of the manifest. I also threw in the file name and the bytes for good measure. This is output in Sandcastle logs and can help identify mismatches. The filename also means we no longer have to rely on piecing together paths on Sandcastle which is nice.

Reviewed By: nikoant

Differential Revision: D24046464

fbshipit-source-id: dc6dc50eb510a067674166b5fdb11af9cf6762b2

packer/src/types.rs

@@ -44,3 +44,6 @@ impl Display for PackType {
         }
     }
 }
+
+#[derive(Eq, PartialEq, Debug, serde::Serialize)]
+pub struct HashSum(pub String);