isc: restore c7i.12xlarge instance type, copy treescape-media into container

[slabasan]

Description

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Checklist

• If creating a new version of the tutorial, create a new directory at the root of the repository with the relevant name
• Ensure all Docker-related material except for tutorial contents goes in a docker subdirectory
• Update github_ci_matrix.json with (1) the tag you will eventually use for the tutorial Docker images (place in the "tag" field) and (2) the name of the directory for your version of the tutorial (place in the "tutorial_dir" field)