Fix left over termQuery in Keyword fields to be searchable with doc_values

[harshavamsi]

Is your feature request related to a problem? Please describe.
Coming from #7057, there is a left over termQuery that needs to be searchable when only doc_values are enabled.

Describe the solution you'd like
Similar to the work done for term queries in #11209, override term query and then handle all three cases when index and doc_values are enabled/disabled.

Describe alternatives you've considered
Do nothing.

[kiranprakash154]

Hi, are we on track for this to be released in 2.12 ?

[harshavamsi]

Hi @kiranprakash154 we determined that this is something that we don't see making any impact, so we scrapped this.

[msfroh]

@harshavamsi -- Does it make sense to still handle the DV-only case? That is, skip the IndexOrDocValuesQuery case (using the indexed query whenever we can).

That is, we wouldn't want to do this as a performance optimization, but we could handle term queries on a non-indexed keyword field that has doc values. I'm imagining a case where there's a kw field that (almost) never gets queried, but does get aggregated over, so we just have doc values. If you do want to query it rarely (or at least filter on it), you could do that as a DV lookup.