feat(NODE-6416)!: drop callback support from public API

[baileympearson]

Description

Summary of Changes

This PR removes callback support from kerberos.

Notes for Reviewers

Some notes on non-obvious changes:

1. Now that Node20 is our MSNV (minimum supported Node version), we can use fetch in our tests. I adjusted the tests to use fetch, and removed the dependency on request.
2. After looking over the win32 tests, I determined that they add no additional value. These tests are not testing windows specific functionality and they don't actually run in CI right now. Instead, they execute the mongodb kerberos authentication manually. We have kerberos tests in the driver, and we plan to add better testing on macos and windows in Modernize Kerberos. I chose to remove these tests but will reconsider if the team wants to keep them.

What is the motivation for this change?

Release Highlight

Release notes highlight

Double check the following

• Lint is passing (npm run check:lint)
• Self-review completed using the steps outlined here
• PR title follows the correct format: type(NODE-xxxx)[!]: description
  • Example: feat(NODE-1234)!: rewriting everything in coffeescript
• Changes are covered by tests
• New TODOs have a related JIRA ticket