Add auto-closing for web browser authentication windows

[wenzel-k24]

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.

   Fixes SNOW-3168502: Add auto-closing for web browser authentication windows #2774

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.
   My change updates the HTML “success” response served by the local callback server in the externalbrowser SSO flow. Instead of leaving the page open indefinitely, the response now includes a small JavaScript snippet that attempts to close the browser window automatically a few seconds after the SAML token is received and the connector has progressed past _process_get/_process_post.

After successful authentication, the user sees the same confirmation message, but the window/tab will auto-close after ~5 seconds.
If the browser blocks window.close(), the page still shows clear instructions so the user can close it manually.
No auth logic changes: token handling and request processing remain the same; only the callback success page behaviour is improved, reducing leftover windows and making the flow smoother for repeated logins.

4. (Optional) PR for stored-proc connector:

[github-actions]

All contributors have signed the CLA ✍️ ✅
_{Posted by the CLA Assistant Lite bot.}

[wenzel-k24]

I have read the CLA Document and I hereby sign the CLA

[sfc-gh-turbaszek]

Please add appropriate change log entry to DESCRIPTION.md

[wenzel-k24]

@sfc-gh-turbaszek done