Previously if the size of the search request was greater than zero we would not cache the request in the request cache.
This change retains the default behaviour of not caching requests with size > 0 but also allows the `request_cache=true` query parameter
to enable the cache for requests with size > 0
In order to be more consistent with what they do, the query cache has been
renamed to request cache and the filter cache has been renamed to query
cache.
A known issue is that package/logger names do no longer match settings names,
please speak up if you think this is an issue.
Here are the settings for which I kept backward compatibility. Note that they
are a bit different from what was discussed on #11569 but putting `cache` before
the name of what is cached has the benefit of making these settings consistent
with the fielddata cache whose size is configured by
`indices.fielddata.cache.size`:
* index.cache.query.enable -> index.requests.cache.enable
* indices.cache.query.size -> indices.requests.cache.size
* indices.cache.filter.size -> indices.queries.cache.size
Close#11569
Colin Goodheart-Smithe
Martijn van Groningen
Clinton Gormley
Adrien Grand