ci: cache clippy job (foundry-rs#5615)

Author: DaniPopes

.github/workflows/test.yml

@@ -266,6 +266,7 @@ jobs:
         steps:
             - uses: actions/checkout@v3
             - uses: dtolnay/rust-toolchain@clippy
+            - uses: Swatinem/rust-cache@v2
             - run: cargo clippy --workspace --all-targets --all-features
               env:
                   RUSTFLAGS: -Dwarnings