[ES|QL] Implements one-line pretty printing of the AST

[vadimkibana]

Summary

Partially addresses #182257

Add a helper function, which given an ES|QL AST formats it to a one-line string.

Checklist

Delete any items that are not applicable to this PR.

• Unit or functional tests were updated or added to match the most common scenarios

For maintainers

• This was checked for breaking API changes and was labeled appropriately

[elasticmachine]

Pinging @elastic/kibana-data-discovery (Team:DataDiscovery)

[elasticmachine]

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

[kibana-ci]

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• Commit: 025d502

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[drewdaemon]

Super cool!