Introduce workspace upgrade summary, rework step result reporting, workspace update

Closes #193 (closed)

Features:

• Models StepResult as general information about what the outcome of a step was
• Implements returning step results in each step
• Implements handling step results in axii w update and in axii w upgrade (print upgrade summary)
• Print headings for each "all modules at once"-step, i.e., "env", "system", "conclude"

Examples

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