Introduced explicit index resolution API

[nibix]

Description

This introduces a new method that allows TransportAction implementations to report the indices the will actually operate on via a standard API to any ActionFilter implementation. This can be then used for example by access control filters to check authorization.

This has several advantages:

• Actually, the way transport actions interpret indices specified in IndicesRequests is extremely diverse. Some do resolution of all expressions and rely on index options, some do resolution of all expressions and modify index options, some do only date math expression resolution, and some do no resolution at all. This change makes gives a method to make it very explicit which indices will be touched by an action.
• Actually, the case where no resolution happens at all is quite common - that's the case for most shard-based actions. This allows us to avoid a costly resolution for all these cases. This should give a significant performance boost.

Note: This is not complete yet and is intended only as a sneak-peek.

Related Issues

Resolves #[Issue number to be closed when this PR is merged]

Check List

• Functionality includes testing.
• API changes companion pull request created, if applicable.
• Public documentation issue/PR created, if applicable.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.
For more information on following Developer Certificate of Origin and signing off your commits, please check here.