Support KVNamespaceListOptions on /data endpoints

[whoabuddy]

There are a few things this would expose to through the API that would be useful:

• cursor: string to pass if the list isn't complete and additional calls have to be made
• prefix: string to filter the list of keys before they're returned instead of after
• limit: less important, but might as well be thorough

These could be processed as query parameters and are not required for a single query.