add x509 test

[nammn]

Summary

This pull request introduces a new end-to-end test suite for VM migration with X509 authentication and TLS.

Test coverage and task integration:

• Added a comprehensive new test file vm_migration_x509.py for VM migration scenarios using X509 client authentication and TLS, covering deployment, TLS setup, X509 authentication, migration, and promotion/pruning steps.
• Registered the new test as a task e2e_vm_migration_x509 in .evergreen-tasks.yml for patch runs.
• Included the new task in the e2e_enterprise_tls_and_x509 task group in .evergreen.yml to ensure it runs alongside related enterprise tests.

Proof of Work

• that new migration x509 test passes

Checklist

• Have you linked a jira ticket and/or is the ticket in the title?
• Have you checked whether your jira ticket required DOCSP changes?
• Have you added changelog file?
  • use skip-changelog label if not needed
  • refer to Changelog files and Release Notes section in CONTRIBUTING.md for more details