Implement suggestions for unknown features in workspace

Author: In-line

Cargo.toml

@@ -67,6 +67,7 @@ clap = "2.31.2"
 unicode-width = "0.1.5"
 openssl = { version = '0.10.11', optional = true }
 im-rc = "15.0.0"
+itertools = "0.10.0"
 
 # A noop dependency that changes in the Rust repository, it's a bit of a hack.
 # See the `src/tools/rustc-workspace-hack/README.md` file in `rust-lang/rust`