[ES|QL] Provide a quick fix to generate a ES|QL control over unrecognized variables

[dej611]

Describe the feature:

The only ways to generate a ES|QL control is either via autocomplete OR in the future via some dashboard clicking flow

If user pastes an existing query with a variable, and this variable is not mapped yet by any existing control, each variable in the query needs to be "rewritten" in order to kick off the autocomplete creation flow again.
In order to solve this it would be nice to use the "Quick fix" feature in the editor and provide a way to generate a control as a "fix" for the "unknown field" error for a variable.

Describe a specific use case for the feature:

This is convenient when the user is pasting a query using variables into the editor directly without using autocomplete.

[elasticmachine]

Pinging @elastic/kibana-esql (Team:ESQL)