Upgrade Codecov, and use a Codecov token (#112)

* Bump codecov/codecov-action from 3.1.4 to 4.5.0

Bumps [codecov/codecov-action](https://github.com/codecov/codecov-action) from 3.1.4 to 4.5.0.
- [Release notes](https://github.com/codecov/codecov-action/releases)
- [Changelog](https://github.com/codecov/codecov-action/blob/main/CHANGELOG.md)
- [Commits](codecov/codecov-action@eaaf4be...e28ff12)

---
updated-dependencies:
- dependency-name: codecov/codecov-action
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

* Use CODECOV_TOKEN

---------

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

.github/workflows/ci.yml

@@ -67,9 +67,12 @@ jobs:
 
       - uses: julia-actions/julia-processcoverage@03114f09f119417c3242a9fb6e0b722676aedf38
 
-      - uses: codecov/codecov-action@eaaf4bedf32dbdc6b720b63067d99c4d77d6047d
+      - uses: codecov/codecov-action@e28ff129e5465c2c0dcc6f003fc735cb6ae0c673
         with:
           file: lcov.info
+          token: ${{ secrets.CODECOV_TOKEN }}
+          fail-ci-if-error: true
+
 
       - name: Verify that test output file exists
         run: test -f "$HOME/julia-runtest"