ArrayExtension preserves keys

[mecha]

Fixes #6

[XedinUnknown]

Is this really better than just array_map()?

Not quite sure. Maybe, resolveDeps() should return a map with keys preserved, and it's just a matter of array_values() to turn it into function args?

[mecha]

That would work. I wanted to keep the current resolveDeps() because I can see its utility. Given ["foo", "bar"] it returns ["foo" => ..., "bar" => ...], which makes a lot of sense. This is why I added a new method. A consumer may want to access the services by their key after passing them through resolveDeps().

On the other hand, there is nothing that is currently utilizing the service keys in the resolveDeps() return value. And realistically, there may not be. Given that this trait is used for service helpers, it's unlikely that individual services will be extracted from the returned array. So it could be changed to preserve the keys in the argument array.

But if we're going to do that, I think we could just use array_map. The immediately-invoked function and the creation of a Generator becomes obsolete and unnecessary.