add rust-toolchain & rust-cache to workflow

.github/workflows/rust.yml

@@ -16,6 +16,10 @@ jobs:
 
     steps:
     - uses: actions/checkout@v4
+    - uses: dtolnay/rust-toolchain@stable
+    - uses: Swatinem/rust-cache@v2
+      with:
+        cache-on-failure: true
     - name: Build
       run: cargo build --verbose --workspace
     - name: Run tests