port `overmind terraform plan/apply` to PTerm

[DavidS-ovm]

migrate overmind terraform plan/apply to PTerm to evaluate its suitability for the most complex of our use-cases.

• runPlanTask
• fix ensureToken prompt to not conflict with the spinner
• submitPlanTask
• snapshotTask
• approve Plan Form
• revlinkWarmupTask
• show plan
• show risk
• runApplyTask
• fix extracted resource display
• fix spinner indentation for nested tasks
• re-add running source display when starting up
• fix "Starting Change:" display leaking into terraform apply output
• show actual commands run

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• integrate logrus output into PTerm writers
• fix cmdSpan shenanigans #574
• upstream cli/custerm/spinner_printer.go to pterm/pterm