`ArrayExtension` does not preserve keys

[mecha]

The ArrayExtension extension class' behavior changed in 0f9ad94, when the resolution of dependencies was extracted into a trait.

Previously, the resolution involved a simple array_map (source here).

After 0f9ad94, ArrayExtension used the newly extracted resolveKeys() trait method, which specifically only returns array values (source here)

Therefore, in order to preserve the previous functionality, ArrayExtension should therefore use resolveDeps() to preserve the dependency array keys.

[mecha]

Correction: resolveDeps() does not preserve the keys in the $keys argument. So a new method must be introduced in the ResolveKeysCapableTrait ... sigh

Is this really better than just array_map()?