Have a simple command line to wait for specific status changes on specific work requests or workflows

Such a command could simplify some of the integration tests, and would also be handy for heavy command line users that want a CLI-based solution to get notified when a work request completes.

Without committing to this design, a command like debusine work-request wait WORK-REQUEST-ID/EVENT could fit the bill (when EVENT is not specified it waits for the end of the work request, either COMPLETED or ABORTED). It could become more elaborate over time depending on the needs (cover more events, wait for multiple work requests, wait for the first of multiple work request, execute a command upon any status change, etc.)

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Initial issue:

Title: debusine on-work-request-completed support limit to a specific work request or workflow

This would allow notifications once my work request is done.