ESQL: Renaming the grouping field before a stats still relies on the original field

[costin]

Description

A potential bug in CombineProjections:
from employees | rename gender AS foo | stats bar = count(*) by foo | drop foo | sort bar - the stats still refers to the original field (gender) for grouping which is problematic as the field no longer exists in the child.
Related to #105433

[elasticsearchmachine]

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

[wchaparro]

@fang-xing-esql still worth doing?

[fang-xing-esql]

@fang-xing-esql still worth doing?

Thanks for the reminder @wchaparro ! It seems like this issue has been fixed, I tried this query below on the recent main, could be the side effects of the other bug fixes. I'll close this bug.

+ curl -u elastic:password -X POST 'localhost:9200/_query?format=txt&pretty' -H 'Content-Type: application/json' '-d
{
  "query": "from sample_data | rename client.ip AS foo | stats bar = count(*) by foo | drop foo | sort bar"

}
'
      bar      
---------------
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1              
1              
4