Allow for Entry to Debug Encryption Key

Liam asked me to raise this as a request.

The debugger does not have a way to handle entering a encryption key to view the source during debug/service entry points.

Start by tracing the debugger's service entry points and how it currently handles encrypted source during debugging. Confirm the expected encryption-key prompt and the source-viewing flow with the maintainer; done means the key can be entered and encrypted source is viewable through those entry points.

Written by the indexing model from the issue text.