Throw an InvalidOperationException for purge requests on running orchestrations

[sophiatev]

Summary

What changed?

This PR introduces throwing an InvalidOperationException when a purge is requested on an individual instance ID for an orchestration that is in an invalid runtime status (i.e. something non-terminal like "Running" or "Pending")

Why is this change needed?

I've run into a lot of customer issues recently related to attempting to purge running orchestrations.

Project checklist

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• All required tests have been added/updated (unit tests, E2E tests)
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[andystaples]

lgtm