[Lens] Formula: KQL autocomplete in formula

[flash1293]

KQL autocomplete is a nice UX and makes it very easy to create the right query without typos. It would be helpful to have the same level of autocomplete when typing KQL in the formula. To do this, the autocomplete logic (without the UI) has to be hooked into the autocomplete API of monaco.

The suggestion functionality is exposed in the data plugin data.autocomplete.getQuerySuggestions()

[elasticmachine]

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

[wylieconlon]

One of the problems we'll need to solve here is that KQL uses double quotes pretty often, so we'll need to avoid conflicts. Another issue is that the KQL syntax accepts a wider range of characters than tinymath does so far.

Monaco autocompletion can handle the async part because of its cancellation token, which is important because KQL autocompletion is usually pretty slow.

[flash1293]

Part of #99297