### Body

We had an issue where extra link class (`AIPlatformConsoleLink`) was removed in [PR](https://github.com/apache/airflow/pull/26836) without removing the class from the `provider.yaml` extra links this resulted in web server exception as shown in https://github.com/apache/airflow/pull/28449


**The Task:**
Add validation that classes of extra-links in provider.yaml are importable

### Committer

- [X] I acknowledge that I am a maintainer/committer of the Apache Airflow project.
print("Checking doc files")
    current_doc_urls: list[str] = []
    current_logo_urls: list[str] = []
    for provider in yaml_files.values():
        if "integrations" in provider:
            current_doc_urls.extend(
                guide
                for guides in provider["integrations"]
                if "how-to-guide" in guides
                for guide in guides["how-to-guide"]
            )
            current_logo_urls.extend(
                integration["logo"] for integration in provider["integrations"] if "logo" in integration
            )
        if "transfers" in provider: