Ordered Query Builder

[jasonvarga]

This fixes the issue where the new entries query builder augmentation (#5238) wouldn't maintain the order you picked.
i.e. In the control panel you intentionally pick entries in a specific order, and it wouldn't output them in that order. Now it will.

Adds an "ordered" query builder decorator.

It wraps up a query builder with a custom order. If you don't call orderBy on it, it'll apply the custom order when retrieving the items.

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In database-land, you could do a raw orderby query, like this:

->whereIn('id', [4, 2, 5])
->orderByRaw("FIELD(id, 4, 2, 5)")

...but we don't support that, and it would be way more effort to do it than this decorator class.