Clean up messy default connection overrides in provider tests

[amoghrajesh]

While working on https://github.com/apache/airflow/pull/52129/files, i saw this pattern in many places.

Pattern of this type:

    @provide_session
    def setup_method(self, method, session=None):
        conn = session.query(Connection).filter(Connection.conn_id == DEFAULT_CONN_ID).first()
        conn.host = HOST
        conn.schema = None
        conn.port = None
        conn.login = None
        conn.password = None
        conn.extra = json.dumps({"token": TOKEN, "host": HOST})

        session.commit()

        self.hook = DatabricksHook()

We should not be overriding default connections this way at ALL, it will make migration of providers to use task sdk extremely hard / annoying. Cleaning up that pattern to use the fixture introduced in #51930

I am introducing a way for tests to only use connections from env via #52129, which will follow this one

---

^ Add meaningful description above
Read the Pull Request Guidelines for more information.
In case of fundamental code changes, an Airflow Improvement Proposal (AIP) is needed.
In case of a new dependency, check compliance with the ASF 3rd Party License Policy.
In case of backwards incompatible changes please leave a note in a newsfragment file, named {pr_number}.significant.rst or {issue_number}.significant.rst, in airflow-core/newsfragments.