### 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.
current_doc_urls.extend(
                op["how-to-guide"] for op in provider["transfers"] if "how-to-guide" in op
            )
    expected_doc_urls = {
        f"/docs/{f.relative_to(DOCS_DIR).as_posix()}"
        for f in DOCS_DIR.glob("apache-airflow-providers-*/operators/**/*.rst")
        if f.name != "index.rst" and "_partials" not in f.parts
    } | {
        f"/docs/{f.relative_to(DOCS_DIR).as_posix()}"
        for f in DOCS_DIR.glob("apache-airflow-providers-*/operators.rst")
    }
    expected_logo_urls = {
        f"/{f.relative_to(DOCS_DIR).as_posix()}"
        for f in DOCS_DIR.glob("integration-logos/**/*")
        if f.is_file()
    }
    try:
        print(" -- Checking document urls: expected (left), current (right)")
        assert_sets_equal(set(expected_doc_urls), set(current_doc_urls))
        print(" -- Checking logo urls: expected (left), current (right)")
        assert_sets_equal(set(expected_logo_urls), set(current_logo_urls))
    except AssertionError as ex:
        print(ex)
        sys.exit(1)
def check_unique_provider_name(yaml_files: dict[str, dict]):
    provider_names = [d["name"] for d in yaml_files.values()]
    duplicates = {x for x in provider_names if provider_names.count(x) > 1}
    if duplicates:
        errors.append(f"Provider name must be unique. Duplicates: {duplicates}")
def check_providers_are_mentioned_in_issue_template(yaml_files: dict[str, dict]):