[Lens] [Visualize] Formatting last_value/top_hits metric for array values

[mbondyra]

Right now, both Visualize and Lens (in progress) don't format array values for top hits aggregation and sometimes it looks quite ugly (see screenshot below). Maybe it's ok, but I'd like this issue to be a starting point for conversation – maybe we want to add a custom formatter for these values? Do we want to leave it as it is? What's the priority of it?

[elasticmachine]

Pinging @elastic/kibana-app (Team:KibanaApp)

[mbondyra]

Closing as it looks much better now: