[BUG] Result of Q29 is incorrect without composite aggregation paginating

[LantaoJin]

What is the bug?
The results of following PPL queries are incorrect due to miss composite aggregation paginating:
Q29 and its plan
Q42 and its plan

Q29

| stats bucket_nullable=false avg(length(Referer)) as l, count() as c, min(Referer) by k
| where c > 100000

This query is pushed down to composite aggregate then filter the aggregation results (10000 rows) in memory.

Q42

| stats bucket_nullable=false count() as PageViews by WindowClientWidth, WindowClientHeight
| sort - PageViews
| head 10 from 10000

This query return empty because it is pushed down to multi-terms aggregation with default 10000 rows then head 10 row from offset 10000.

Do you have any additional context?
#4519
#4760