The governing bodies of a third class county and the political subdivision constituting the county seat or the county acting alone may create a body corporate and politic to be named the ......... County Convention Center Authority to be created as a public authority and government instrumentality to have continuing succession until its existence shall be terminated by law. If the convention center to be constructed by an authority created under this subdivision shall be located within the jurisdictional limits of the county seat of the county, the authority shall be a joint authority of the county and the county seat. If the convention center shall be located outside the jurisdictional limits of the county seat of the county, the authority may be created solely by the county. The exercise by the authority of the powers conferred by this subdivision is hereby declared to be and shall for all purposes be deemed and held to be the performance of an essential public function.