Utilize IIT 3.0 config fixture across test modules

[dviggiano]

use_iit_3_config fixture added to the following modules & methods:

test_big_phi.test_clear_subsystem_caches_after_computing_sia_config_option() test_compute_network.test_all_complexes_parallelization() test_json.test_json_deserialization() test_json.test_deserialization_memoizes_duplicate_objects()*

*test still not passing due to additional error(s)

ValueErrors related to IIT 3.0 requirements no longer thrown