[GuideLLM Refactor] Fixes for asyncio and timezone tests

[sjmonson]

Summary

Default to marking tests that timeout as XFAIL.

Details

• [ ]

Test Plan

Related Issues

• Closes [GuideLLM Refactor] fix tests in ci #404

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Use of AI

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• Includes AI-generated tests (NOTE: AI written tests should have a docstring that includes ## WRITTEN BY AI ##)

[jaredoconnell]

Looks good. Unfortunate that we need to ignore those failures, but the tests take too long on CI. Literally at least 10 times as long.