ESQL: high count fields sorting removal

[bpintea]

Description

When analysing a query on thousands of fields, sorting these can take a significant chunk of time of the Analyzer (% goes up with fields count).
This is visible in simple queries already (FROM pattern).

The question of usability of a response containing Ks of fields aside, we could consider dropping sorting the fields, should the count be over a given threshold (1K) for improved responsiveness (the user can then still search through the list, by a pattern, in the UI).

[elasticsearchmachine]

Pinging @elastic/es-analytical-engine (Team:Analytics)