### 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.
try:
        difference1 = set1.difference(set2)
    except TypeError as e:
        raise AssertionError(f"invalid type when attempting set difference: {e}")
    except AttributeError as e:
        raise AssertionError(f"first argument does not support set difference: {e}")
    try:
        difference2 = set2.difference(set1)
    except TypeError as e:
        raise AssertionError(f"invalid type when attempting set difference: {e}")
    except AttributeError as e:
        raise AssertionError(f"second argument does not support set difference: {e}")
    if not (difference1 or difference2):
        return
    lines = []
    if difference1:
        lines.append("    -- Items in the left set but not the right:")
        for item in sorted(difference1):
            lines.append(f"       {item!r}")
    if difference2:
        lines.append("    -- Items in the right set but not the left:")
        for item in sorted(difference2):
            lines.append(f"       {item!r}")
    standard_msg = "\n".join(lines)
    raise AssertionError(standard_msg)
def check_if_objects_belongs_to_package(