FIXME CI: Avoid using abandoned actions-rs/toolchain

See https://github.co m/actions-rs/toolchain/issues/216#issuecomment-1291613319
and https://github.co m/actions-rs/toolchain/issues/221#issuecomment-1531857380

.github/workflows/lint_and_test.yml

@@ -26,11 +26,11 @@ jobs:
           python-version: '3.x'
       # Intentionally don't do system updates – let's try to keep this small and fast, if at all possible.
       - name: Install latest stable rust toolchain
-        uses: actions-rs/toolchain@v1
-        with:
-          toolchain: stable
-          default: true
-          override: true
+        # Can't use actions-rs/toolchain@v1: It's outdated (three years old), and uses the about-to-be-removed "set-output" hack to output to Github Actions
+        run: |
+          curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs > /tmp/install_rust.sh
+          chmod +x /tmp/install_rust.sh
+          /tmp/install_rust.sh -y
       - name: Install black
         # The setup-python action set default python to python3.x. Note that we are not using system python here.
         run: |