Improve Codecov configuration (#1103)

Author: akx

.github/workflows/ci.yml

@@ -63,6 +63,9 @@ jobs:
     - uses: codecov/codecov-action@v4
       with:
         directory: ${{ runner.temp }}
+        flags: ${{ matrix.os }}-${{ matrix.python-version }}
+        token: ${{ secrets.CODECOV_TOKEN }}
+        verbose: true
   build:
     runs-on: ubuntu-22.04
     needs: lint