test: Delete clusters and collateral after integration tests

[c-ryan-k]

Instead of an optional cleanup job (which was previously optional due to instability) this modifies our integration tests to use az iot ops delete to clean up cluster resources after integration tests complete.

It also removes the cleanup parameter from our integration tests (and documentation) since this behavior is now automatic.

Example run here: https://github.com/c-ryan-k/azure-iot-ops-cli-extension/actions/runs/9490745909/job/26154856276#step:27:45

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