When using ElasticSearch 7.8, logs queries return no data

[idastambuk]

What happened:
Originally reported here.
The problem is in this line, when according to ElasticSearch docs for v7, format fields should be sent as docvalue_fields (https://www.elastic.co/guide/en/elasticsearch/reference/7.17/search-fields.html#docvalue-fields)

What you expected to happen:

How to reproduce it (as minimally and precisely as possible):

Anything else we need to know?:

Environment:

• Grafana version:
• OpenSearch version:
• Plugin version: