Reported in https://github.com/mongodb-js/vscode/issues/273

Currently it's not apparent that running a playground in the extension returns only the first 20 results when the last item in a playground is a cursor. This is the default mongosh behavior, however it can be confusing for someone new to the tools. This ticket involves updating the playground template to ensure we're transparent in the batch size and cursor usage.

While we're updating that let's also update the description of the `mdb.defaultLimit` setting to make it clear that that setting only applies to the documents shown from the explorer tree (not playground results).