Extend _cat/indices with storage type to simplify index management

[sandervandegeijn]

Is your feature request related to a problem? Please describe.
With the implementation of searchable snapshots there are now multiple storage types. For index management purposes it would be helpful it the _cat/indices exposed the storage type.

Describe the solution you'd like
Extend _cat/indices with storage type

Describe alternatives you've considered
Getting the settings of all individual indices. Works but it's not convenient

Additional context
none

[tlfeng]

Thanks for requesting the feature, it's under the consideration. There is a related request in #6528 (comment) which I summarized in #7332 (comment).

[sandervandegeijn]

Great summary, that covers it way better :)

[anasalkouz]

Closing this on behalf of #6528