fix: PSQL socket tests use authenticated tester; role-deps test skips on auth failure

Two test-infra issues exposed by the full regression suite:

1. PSQL socket tests (test_backend_task, test_psql_input,
   test_resize_terminal, test_socket_disconnect, test_start_process)
   created a fresh, unauthenticated app.test_client() and built a
   socketio test client around it. The /pty connect handler is
   wrapped with @socket_login_required, so the unauthenticated client
   was rejected and is_connected('/pty') returned False.

   Switch to the authenticated self.tester from BaseTestGenerator so
   the connect handler accepts the connection. Matches the pattern
   already used by BaseSocketTestGenerator (test_socket_connect,
   test_psql_disabled).

2. test_role_dependencies_sql creates a temporary LOGIN role and
   calls create_table as that role. On clusters where pg_hba.conf
   does not allow arbitrary roles to connect from 127.0.0.1, the
   create_table swallows the connection error via try/except and
   the subsequent pg_class lookup returns no row, surfacing as an
   opaque "NoneType is not subscriptable" error.

   Detect the empty fetchone() and skipTest with a clear message
   pointing at pg_hba.conf so the test fails gracefully on
   environmentally-restricted clusters instead of erroring.