Check for unused deps in CI (#1262)

* Check for unused deps in CI

* Bump slashing protection parking_lot version

.github/workflows/test-suite.yml

@@ -121,3 +121,14 @@ jobs:
    - uses: actions/checkout@v1
    - name: Run cargo audit to identify known security vulnerabilities reported to the RustSec Advisory Database
      run:  make audit
+  cargo-udeps:
+   runs-on: ubuntu-latest
+   needs: cargo-fmt
+   steps:
+   - uses: actions/checkout@v1
+   - name: Get latest version of nightly Rust
+     run: rustup update nightly
+   - name: Install cargo-udeps
+     run: cargo install cargo-udeps --locked
+   - name: Run cargo udeps to identify unused crates in the dependency graph
+     run: make udeps