Address mdtest examples not yet convertible to Playground presentation

[philrz]

The changes in #5489 converted the majority of docs examples from mdtest-command to mdtest-spq which enabled them to be rendered in the interactive "Playground" style on the new SuperDB docs site. However, as I was making my way through all the examples I came across a fair number that didn't fit into the current approach and these remain mdtest-command for now.

These examples come in varied forms. There are some that probably should remain mdtest-command examples for defensible reasons, e.g., the examples in the first 1/3 of the super command doc, since by design they're trying to show how to use the command at the CLI, so switching these over to interactive examples that run in the browser probably wouldn't make sense. OTOH there are many other examples that would surely be best presented as interactive examples, but we'd just need enhancements to mdtest-spq and/or the Playground rendering code to enable it.

Since the remaining mdtest-command examples are a minority, it's understood that it may not make sense now/ever to put in significant effort to get to 100% coverage for every example that might benefit. However, on the assumption that we want to work over time toward consistent/sophisticated presentation of the docs, I'll be opening issues linked to this Epic that cite the examples that might benefit from enhancement and we can discuss as a group whether we address them now/later/never and how. As I've spent some time staring at these already, I'll seed the issues with some ideas of my own of how we might go about attacking, but I respect that those who are closer to the code may have other/better ideas.