Currently, the test suite assumes the URI includes multiple hosts and conditionally reduces it to a single host (see: FunctionalTestCase::getUri()). This mainly applies to useMultipleMongoses in spec tests.

For load balancer tests, there may be entirely different URIs for multi-server and single-server environments, so that logic does not apply. LB tests currently run exclusively with the single-server URI. We should also provide the multi-server URIs to the test suites (i.e. MULTI_LB_MONGOS_URI for Load Balancer Testing) and conditionally use those for tests where useMultipleMongoses is true.

Additionally, we can revisit how useMultipleMongoses is handled/enforced for non-LB spec tests. We should confirm that existing tests do use single-mongos URIs by default and that a multi-mongos URI is both available and required when useMultipleMongoses is true.