feature(gradle-test): provide ablity for indexes provides by third party lib.

[DarkWeird]

Description

This PR resolves problem with adding TeraNUI v3.
You should not add gestalt v8 deps for TeraNUI's core module. only for nui-gestalt-di lib.

Usage:

/**
 * Index redirects for dependents libs/games.
 * Requires gestalt-di's annotation processing for dependents builds.
 */

@IndexInherited
@BindAnnotationFor(UIWidget.class)
abstract class UIWidgetIndex {
}

@IndexInherited
@BindAnnotationFor(UILayout.class)
abstract class UILayoutIndex {

}

@IndexInherited
@BindAnnotationFor(CopyStrategy.class)
abstract class CopyStrategyIndex {

}

Limitations:

1. This works for any dependents libs with gestalt-di dep. not dependecies. (there can be resolved with Index task)

[soloturn]

@BenjaminAmos is this still necessary?

[BenjaminAmos]

The original intent for this pull request is obsolete since it was decided that gestalt-inject was minimal enough at the time to make it a dependency of NUI 4.0 (unreleased). Being able to define indexes on behalf of a third-party library may still be useful functionality though.