Add support for lumen explain --list

[jnsahaj]

I would like to move lumen list to lumen explain --list

Reason: The explain command supports --query already, and later on explain might get more features (think: chat). This change will ensure consistency of features. --list will become a way to "get the input to explain"

For now, the lumen list command will stay, and can be deprecated in v2.
Its mentions will be removed from the docs