SNOW-996732: improve clean up logic of connection

[sfc-gh-aling]

Please answer these questions before submitting your pull requests. Thanks!

1. What GitHub issue is this PR addressing? Make sure that there is an accompanying issue to your PR.

   the __del__ method is unstable and gets called at random timing. in one of the recent report, we found the __del__ is causing circular import issue.

as a short term fix, we fix by moving away from __del__ method to using atexit to clean up connection at intepreter shutdown time.

long term fix plan here: SNOW-1218851

2. Fill out the following pre-review checklist:

   • [ ] I am adding a new automated test(s) to verify correctness of my new code
   • [ ] I am adding new logging messages
   • [ ] I am adding a new telemetry message
   • [ ] I am modifying authorization mechanisms
   • [ ] I am adding new credentials
   • [ ] I am modifying OCSP code
   • [ ] I am adding a new dependency

3. Please describe how your code solves the related issue.

   Please write a short description of how your code change solves the related issue.

[sfc-gh-bwarsaw]

As mentioned in Slack: One thing to keep in mind is that atexit handlers don't get run if os._exit() is called or the process crashes.

[sfc-gh-aling]

thanks @sfc-gh-bwarsaw , this should not be a concern to our connector as we didn't perform critical job during the closing stage.