### 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 connection classes belong to package")
    resource_type = "hook-class-names"
    for yaml_file_path, provider_data in yaml_files.items():
        provider_package = pathlib.Path(yaml_file_path).parent.as_posix().replace("/", ".")
        hook_class_names = provider_data.get(resource_type)
        if hook_class_names:
            check_if_objects_belongs_to_package(
                hook_class_names, provider_package, yaml_file_path, resource_type
            )
def check_duplicates_in_list_of_transfers(yaml_files: dict[str, dict]):
    print("Checking for duplicates in list of transfers")
    errors = []
    resource_type = "transfers"
    for yaml_file_path, provider_data in yaml_files.items():
        resource_data = provider_data.get(resource_type, [])
        source_target_integrations = [
            (r.get("source-integration-name", ""), r.get("target-integration-name", ""))
            for r in resource_data
        ]
        if len(source_target_integrations) != len(set(source_target_integrations)):
            for integration_couple in source_target_integrations:
                if source_target_integrations.count(integration_couple) > 1:
                    errors.append(
                        f"Duplicated content of \n"
                        f" '{resource_type}/source-integration-name/{integration_couple[0]}' "
                        f" '{resource_type}/target-integration-name/{integration_couple[1]}' "
                        f"in file: {yaml_file_path}"
                    )
def check_invalid_integration(yaml_files: dict[str, dict]):