[Lens] Identify and fix performance bottlenecks with large index patterns

[mbondyra]

The goal of this issue is to gather the circumstances of where Lens becomes too slow to being used comfortably.
This issue is created to track these situations, decide what to do with them, fix them and find a strategy to make the fixes sustainable (eg performance testing).

Known cases:

• loading big index patterns like filebeat-* (more than 4000 fields)

[elasticmachine]

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

[wylieconlon]

Updating the title because there is only one example

[flash1293]

Performance levels should be back to 7.8 levels by #77210 but I think it still makes sense to keep this issue open because it looks like there is still room for improvement. I will move it back to minor bugs though because in most scenarios performance should be acceptable now.

[flash1293]

@mbondyra Reconsidering my stance from last September - is there something we can do right now? If there's not specific plan I would like to close this issue until we come up with concrete steps.

[mbondyra]

Makes sense. Closing.