There are currently only two tests for `storedSource` in the `views/*` directory. At minimum, we should add some more tests for this `$search` feature, ideally on subpipeline `$search` queries.

For maximum coverage, I'm considering turning every applicable test into a function that takes in a `storedSource` parameter and then creates a search index with `storedSource` as specified. Each test function would be called twice, once with `storedSource` and once without it.

This shouldn't be a massive change, as the expected output for both `storedSource` and non-`storedSource` should be exactly the same. The only difference is the explain output as the view definition shouldn't be applied if `storedSource` is true.