ci: print log on test failure and clean cache

.github/workflows/ci.yml

@@ -33,3 +33,8 @@ jobs:
         run: cargo test --verbose --all
       - name: cargo xtask test
         run: cargo xtask test
+      - name: print logs if tests fail
+        run: cat test_log/*.log
+        if: failure()
+      - name: cargo clean cache
+        run: cargo install cargo-cache --no-default-features --features ci-autoclean && cargo-cache