Fixed client hanging when using startup() after stop() a few times, and fixed is_server_connected being always True

[hello-robot-shehab]

Many hours were wasted on clients' zmq hanging for no reason. The bug is caught!

The main culprit appears to be self.context.term() unable to close out zmq sockets until Ctrl+C was pressed. We'd known this gave a zmq exception:

Traceback (most recent call last):
    File "/home/shehab/.local/lib/python3.12/site-packages/zmq/sugar/context.py", line 140, in __del__
      self.destroy()
    File "/home/shehab/.local/lib/python3.12/site-packages/zmq/sugar/context.py", line 322, in destroy
      self.term()
    File "/home/shehab/.local/lib/python3.12/site-packages/zmq/sugar/context.py", line 264, in term
      super().term()
    File "zmq/backend/cython/_zmq.py", line 596, in zmq.backend.cython._zmq.Context.term
      _check_rc(rc)
      ^^^^^^^^^^^
    File "zmq/backend/cython/_zmq.py", line 179, in zmq.backend.cython._zmq._check_rc
      PyErr_CheckSignals()
      ^^^^^^^^^^^
  KeyboardInterrupt

#94 describes a similar behavior with zmq hanging.

Steps to reproduce:

1. The easier way it to run test/test_client_connection.py on the main branch (Note: this file is introduced in this PR, so just copy it to your main and run it!)
2. Run it and notice that it hangs forever until you ctrl+c, which then gives the exception above.
3. Another test that used to not work on main is the test_require_connection.py, this is fixed in this PR.

To test

1. Run test/test_client_connection.py
2. Run test/test_server_connection.py
3. Run test/test_requite_connection.py

And observe that they pass.

[hello-robot-shehab]

I ran into the zmq bug again during REx_camera_calibate.

Okay this was happening because of gc. Added a test for garbage collection, and fixed the hanging by using linger=0