Use snapshots to test `* show` outputs

[kangasta]

This would move inline text manual snapshots into files managed by cupaloy. Makes it easier to manage snapshots without manual copy-pasting and would make it easier to add different snapshots in future (e.g., test output with colors enabled on non-windows environments).

• [ ] account show
• [ ] ip-address show
• [ ] network show
• [ ] router show
• [ ] server firewall show
• [x] server show
• [ ] storage show

db show and lb show do not have "manual" snapshot tests at the moment.