Add live E2E coverage for policies, rules, and lists

[pengfeiye]

License

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Summary:

• Added live, env-gated E2E test suite under tests/e2e for lists, rules, and policies.
• Implemented deterministic cleanup via shared resource registry/finalizers in tests/e2e/conftest.py to avoid orphaned resources.
• Covered full lifecycle flows:
  • Lists: create, find, update, add/list/remove items, destroy
  • Rules: create, find, update, list verification, destroy
  • Policies: create, find, update (including rule association), list verification, destroy
• Hardened tests for real API response shapes by:
  • verifying policy updates with follow-up find when update payload omits id
  • using normalized/raw list ID extraction for list endpoints with variable payload structure
• Registered pytest marker in pyproject.toml:
  • e2e: marks tests that call live Nylas APIs
• Validation:
  • pytest tests/e2e -m e2e passes (3/3)
  • existing unit resource tests remain green