feat(.github): run cargo clippy on each crate individually

> Use cargo-hack to run clippy on each crate individually with its
> respective default features only. Can reveal warnings otherwise
> hidden given that a plain cargo clippy combines all features of the
> workspace. See e.g. #1695.

.github/workflows/check.yml

@@ -153,7 +153,13 @@ jobs:
         if: success() || failure()
 
       - name: Clippy
-        run: cargo +${{ matrix.rust-toolchain }} clippy --all-targets -- -D warnings || ${{ matrix.rust-toolchain == 'nightly' }}
+        run: |
+          # Use cargo-hack to run clippy on each crate individually with its
+          # respective default features only. Can reveal warnings otherwise
+          # hidden given that a plain cargo clippy combines all features of the
+          # workspace. See e.g. https://github.com/mozilla/neqo/pull/1695.
+          cargo +${{ matrix.rust-toolchain }} install cargo-hack
+          cargo +${{ matrix.rust-toolchain }} hack clippy --all-targets -- -D warnings || ${{ matrix.rust-toolchain == 'nightly' }}
         if: success() || failure()
 
       - name: Check rustdoc links