Resolve indices before starting to reindex. This ensures that the list
of indices does not change when failing over (TBD). The one exception to
this is aliases, which we still need to access through the alias.

In addition, resolved index patterns are sorted by create-date and
otherwise the listed order is preserved. This ensures that once we
reindex one index at a time, we will get reasonable time locality for
time based indices.

The resolved list of indices will also by used to do searching one
index (or index group) at a time, improving search performance (since we
use sort) and allowing us to do more fine-grained checkpoint and track
progress (TBD).

Relates elastic#42612

…_resolve_indices

…_resolve_indices

…_resolve_indices