Code coverage tooling is outdated

The library was running the command `npm run report-coverage` to provide test coverage information. However, the command is causing the CI to fail due to the error:

```
==> Uploading reports
(node:1970) [DEP0040] DeprecationWarning: The `punycode` module is deprecated. Please use a userland alternative instead.
(Use `node --trace-deprecation ...` to show where the warning was created)
/home/runner/work/node-httptransfer/node-httptransfer/node_modules/codecov/lib/codecov.js:212
} else if (result.split('\n').length !== 2) {
^

TypeError: result.split is not a function
at /home/runner/work/node-httptransfer/node-httptransfer/node_modules/codecov/lib/codecov.js:212:25
at /home/runner/work/node-httptransfer/node-httptransfer/node_modules/teeny-request/build/src/index.js:217:17
at process.processTicksAndRejections (node:internal/process/task_queues:95:5)
```

Research into `codecov` reveals that it has been deprecated for several years. The script was removed from the CI to unblock development, so the coverage tooling should be updated if coverage statistics are still desired.

Beginne mit der Untersuchung des Skripts npm run report-coverage und der CI-Konfiguration, die es zuvor aufgerufen hat. Überprüfe, wie das veraltete Paket codecov den Upload-Fehler verursacht, und ermittle einen unterstützten Weg zur Übermittlung der Coverage, falls Coverage weiterhin erforderlich ist. Als erledigt gilt die Aufgabe, wenn der Coverage-Workflow ohne die veralteten Tools erfolgreich ausgeführt wird.

Vom Indexierungsmodell aus dem Issue-Text verfasst.