ci: Update codecov action and fail CI if it fails (#2116)

Author: mattrunyon

.github/workflows/unit.yml

@@ -88,8 +88,9 @@ jobs:
           npm run test:golden-layout
 
       - name: Codecov report
-        uses: codecov/codecov-action@v3
+        uses: codecov/codecov-action@v4
         with:
+          fail_ci_if_error: true
           token: ${{ secrets.CODECOV_TOKEN }}
           directory: ./coverage
           flags: unit