[Index Patterns] Allow creation of cross cluster index patterns when cluster is <7.9

[mattkime]

7.9 introduced the resolve api which is used by the UI when creating an index pattern. It determines whether or not there's a match to an index pattern. Cross cluster search is supported by ±1 major version, which means we need to use an api call that works on 6+. The resolve api is necessary for surfacing data streams so we'll fire off two requests - the resolve api and the previously used search request - and merge the results.

We can revert to a single cross cluster request in kibana v9.

[elasticmachine]

Pinging @elastic/kibana-app-arch (Team:AppArch)

[fdartayre]

Thanks for reporting @mattkime, this looks like a bug to me since it prevents from creating CCS index patterns on 7.9 when the remote cluster is in a version without the resolve api (<= 7.8).

[mattkime]

addressed by #80006 in v7.10 and v7.9.3 releases.