lint(validators): support top-level array

[ee7]

So far, none of the files we were linting were an array at the top level. But links.json is.

Some possible future refactorings:

• Use common logic for all the "missing key" conditions.
• Make the arrayOfStrings procs extend the array procs.
• Make the empty string unnecessary in isObject(data, "", path).

This PR is still a bit WIP, and I'm not set on its approach yet. But it might soon be good enough for now.

I need to do the below before I merge this PR:

• Fix the bug that makes configlet lint produce an error
• Verify that this PR does not change the output of configlet lint

[ErikSchierboom]

Nice!

Use common logic for all the "missing key" conditions.
Make the arrayOfStrings procs extend the array procs.
Make the empty string unnecessary in isObject(data, "", path).

Those are all nice refactorings for the future.