Replace Moving Average pipeline aggregation

[timroes]

The moving average pipeline aggregation has been deprecated as of 6.4: https://www.elastic.co/guide/en/elasticsearch/reference/current/search-aggregations-pipeline-movavg-aggregation.html

We need to replace it with the new Moving Function aggregation instead.

This needs to be replaced in

• TSVB ([TSVB] Replace deprecated moving_avg by moving_fn aggregation #36520)
• Kibana aggregations (Replace deprecated moving_avg by moving_fn aggregation #34155)

Timelion's moving average is implemented in the Kibana server, and does not use the moving_avg ES function.

cc @elastic/kibana-app

[markov00]

cc @elastic/kibana-tsvb-external

[markov00]

Hey @timroes, after a first review with @alexwizp on TSVB the refactoring will be a bit more complex.
On TSVB we have UI options for configure some parameters like minimize, predict that are no more available in the moving function (elastic/elasticsearch#29594 for reference)

The question is how to threat those parameters, my ideas are:

• we should remove them from the UI
• we should include a migration that nicely fallback to an existing property/moving function function

How can we make the user aware that, after migration, some visualization may have been changed?

[timroes]

@markov00 I agree with you: Let's remove them from the UI and write a migration that will actually remove them (convert them) from existing saved objects. I think it's enough for us to highlight that in the release notes of the respective version.

[gospodarsky]

Closed #36624