Run cargo fmt --check in CI

Similar to the clang case, check formatting prior to building the
tests.

I noticed a couple of inconsistencies while working on a new test, and
realized that we are not enforcing formatting.

Author: saulecabrera

.github/workflows/compile-tests.yml

@@ -63,6 +63,11 @@ jobs:
           toolchain: stable
           target: wasm32-wasip1
 
+      - name: Run `cargo-fmt`
+        run: |
+          cargo fmt --manifest-path ./tests/rust/wasm32-wasip3/Cargo.toml --check
+          cargo fmt --manifest-path ./tests/rust/wasm32-wasip1/Cargo.toml --check
+
       - name: Build tests
         working-directory: tests/rust
         run: |