[Lens] Render suggestions after main chart

[flash1293]

Right now the main chart and the suggestions start rendering almost at the same time - this can cause a lot Elasticsearch load. By waiting for the main chart and rendering suggestions afterwards, caches can be leveraged better on several levels.

[elasticmachine]

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

[flash1293]

@gingerwizard I prepared a PR for rendering suggestions after the main chart here: #100410

It's still kicking off the un-aggregated 500 document search for the field existence check in parallel - let me know what happens.

[flash1293]

When implementing this we can also get rid of the hardcoded debounce of 2s for rendering of suggestion charts - waiting for the main chart is a much better way of handling this:

kibana/x-pack/plugins/lens/public/editor_frame_service/editor_frame/suggestion_panel.tsx

Line 97 in b35cde5

<ExpressionRendererComponent

[ghudgins]

waiting on @gingerwizard to tell us if we should proceed with this in 7.15 (see #100410)

[flash1293]

As discussed we moved this towards the end because it's not simple to do technically in our current architecture

[stratoula]

We don't rendert the charts in suggestions in recent kibana versions so this is not relevant anymore