[#255] Show stack contents in DAP

Description

[#255] Show stack contents in DAP

Problem: we can display current position on the code, but we also want
the user to see the stack at this moment.

Solution: returns stack contents to VSCode as a single "scope",
displaying lists, maps and other nested structures as nested trees in
the UI.

Related issue(s)

Resolves #255 (closed)

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