CI: split tests

in case of failure the mail only indicate which tests fails,
since the tests don't really reuse artifacts (except the checkout) just split
in three

.github/workflows/ci.yml

@@ -5,13 +5,21 @@ env:
   RUSTFLAGS: "-Dwarnings"
 
 jobs:
-  rust_checks:
+  clippy:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
-      - name: Run rustfmt
-        run: cargo fmt
       - name: Run Clippy
         run: cargo clippy --all-targets --all-features
+  rust_tests:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
       - name: Run tests
         run: cargo test
+  rustfmt:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Run rustfmt
+        run: cargo fmt