This integrates SQL's metadata calls with security by creating
`SqlIndicesAction` and routing all of SQL's metadata calls through
it. Since it *does* know up from which indices it is working against
it can be an `IndicesRequest.Replaceable` and integrate with the
existing security infrastructure for filtering indices.
This request is implemented fairly similarly to the `GetIndexAction`
with the option to read from the master or from a local copy of
cluster state. Currently SQL forces it to run on the local copy
because the request doesn't properly support serialization. I'd
like to implement that in a followup.
Original commit: elastic/x-pack-elasticsearch@15f9512820