[azsdk-cli] Enforce cancellation token usage for async methods

We should add an analyzer just to make sure we're always passing down cancellation tokens for any async methods and/or where we do blocking operations (or call dependencies that take cancellation tokens). I'm not sure this is that simple to do.

The issue names no files, tests, or entry points. First determine where the repository's analyzers are implemented and how existing rules are tested; done means defining and validating the scope for cancellation-token enforcement, including async methods, blocking operations, and token-aware dependencies.

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