ci: run rust-clippy, send results to CodeQL

This adds a new analysis job to run Rust's code quality analyzer,
`rust-clippy`, and upload the JSON results to GitHub's CodeQL service.
This template was suggested by GitHub itself and I've modified it to fit
our repository; let's see how this goes.

.github/workflows/codeql.yml

@@ -71,3 +71,34 @@ jobs:
         uses: github/codeql-action/analyze@e8893c57a1f3a2b659b6b55564fdfdbbd2982911 # v3.24.0
         with:
           category: "/language:${{matrix.language}}"
+
+  analyze_rust:
+    name: Analyze (Rust)
+    runs-on: ubuntu-latest
+    defaults:
+      run:
+        working-directory: rust
+    permissions:
+      contents: read
+      security-events: write
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@b4ffde65f46336ab88eb53be808477a3936bae11 # v4.1.1
+
+      - name: Install dependencies
+        run: |
+          rustup component add clippy
+          cargo install clippy-sarif sarif-fmt
+
+      - name: Run clippy
+        run:
+          cargo clippy
+          --all-features
+          --message-format=json | clippy-sarif | tee rust-clippy-results.sarif | sarif-fmt
+        continue-on-error: true
+
+      - name: Upload analysis
+        uses: github/codeql-action/upload-sarif@v3
+        with:
+          sarif_file: rust-clippy-results.sarif
+          wait-for-processing: true