[Dashboards][Meta] ES|QL controls phase 2

[ghudgins]

In the first phase of ES|QL controls we have enabled the creation of Controls from the editor. The creation is opiniated though which means that the editor decides when to suggest the Create control suggestion

On the second phase we want to make it more prominent to the users and easier to discover. Specifically:

• We want when the user is typing ? to be able to create a control from wherever they are in the editor. We are tracking this here [ES|QL][Variables] Distinguish the identifiers vs values on the query level #209731
• We want the user to be able to create a control first and then attach it wherever they wish. (The flow starts from the controls builder)
• Auto-complete for existing variables

Both are blocked as we havent decided how to distinguish between a static values control and a fields / functions (identifier) type control

[ghudgins]

https://elastic.slack.com/archives/C072RJEBA87/p1739219738502359 - design updates from @andreadelrio