Deprecate/remove common_terms query and cutoff_frequency

[jimczi]

The common_terms query and the cutoff_frequency option of the match query are a good way to speed up search without removing stop words. However in Elasticsearch 7 we have another alternative that can automatically skip non-competitive documents based on the maximum score of each term in the query. This new method doesn't require any configuration (no cutoff frequency) and can be much faster than the common_terms alternative if the total number of hits that matches the query is not tracked.
For this reason I wonder if we could/should deprecate/remove the other alternatives (common_terms and cutoff_frequency), they should not be needed anymore since we have a better alternative that doesn't require to set a cutoff frequency while still being able to speed up queries with high frequency terms.

[elasticmachine]

Pinging @elastic/es-search

[jimczi]

We discussed this offline and agreed that we should deprecate and remove since it is redundant with the MAX_SCORE optimization that will land in Elasticsearch 7.0. It's too late to deprecate in 6.x so the plan is to deprecate these features in 7x and remove in 8.

[ogryniuk]

Hi there,
I am interested in contributing to this project and have two questions:

1. Specific: Does this issue require any actions or is it simply a discussion of things to do in future?
   I would like to work on it but it discusses possible changes to different versions of Elasticsearch and I wonder how to carry them out if this Elasticsearch repository has only one single version...

2. General: How to request an issue to be assigned to you and avoid doing it for nothing which can happen when another contributor also gets interested and commit before you?

[cshtdd]

I created a PR to address this issue

#37511

I'm not sure it is all that is needed.

Can you please review it.