Deny all Clippy warnings (#8720)

This PR makes Clippy deny all warnings across the workspace.

We now enumerate all of the rules that have violations and temporarily
allow them, with the goal being to drive the list down over time.

On Windows we don't yet use `--deny warnings`, as the Windows build
still has some warnings.

Release Notes:

- N/A

.github/workflows/release_nightly.yml

@@ -32,8 +32,7 @@ jobs:
         uses: ./.github/actions/check_style
 
       - name: Run clippy
-        shell: bash -euxo pipefail {0}
-        run: script/clippy
+        run: cargo xtask clippy
   tests:
     name: Run tests
     if: github.repository_owner == 'zed-industries'