Add inspection subtask

[xsc]

We should be able to print:

• build base image
• build user
• build profiles
• cached paths
• ignored paths
• runner settings (image, CMD/ENTRYPOINT)
• build and assemble script contents

Allowing optional JSON output of this information could allow additional tooling to exist, e.g. auto-creation of a Markdown file with usage instructions.

CLI:

into inspect <builder>