Add migrating and troubleshooting to compliance pipeline docs

What does this MR do and why?

This MR creates a section in the Compliance pipeline docs about migrating to pipeline execution policies, this is in anticipation of releasing the migration tool Compliance Pipeline to Security Policy Migration (&11275)

Some customers are already migrating over since the announcement that compliance pipelines are deprecated in 17.3. During this we are receiving questions and blockers. This MR also adds a troubleshooting section to start documenting this exception use cases

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