### 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.
#
#
"""Config sub-commands."""
from __future__ import annotations
import locale
import logging
import os
import platform
import subprocess
import sys
from urllib.parse import urlsplit, urlunsplit
import httpx
import tenacity
from airflow import configuration
from airflow.cli.simple_table import AirflowConsole
from airflow.providers_manager import ProvidersManager
from airflow.typing_compat import Protocol
from airflow.utils.cli import suppress_logs_and_warning
from airflow.utils.platform import getuser
from airflow.version import version as airflow_version
log = logging.getLogger(__name__)
class Anonymizer(Protocol):