CI: Cache cargo-deny (#32543)

Use the `cargo-install` action to cache the cargo-deny output.
`cargo-deny` is currently unconditionally installed during bootstrap,
and takes around 2 minutes to install, so caching should give a
significant speedup

Signed-off-by: Jonathan Schwender <jonathan.schwender@huawei.com>

.github/workflows/mac.yml

@@ -84,6 +84,11 @@ jobs:
         with:
           crate: taplo-cli
           locked: true
+      - name: Install cargo-deny
+        uses: baptiste0928/cargo-install@v3
+        with:
+          crate: cargo-deny
+          locked: true
       - name: Bootstrap
         run: |
           python3 -m pip install --upgrade pip