Update AggregateJsonConverter.cs

[konbur]

If search requests multiple aggregations and there present scripted metric aggregation that returns Map (dictionary), some aggregations absent in Aggregations after json deserializaion

This fixes requires perfrom reader.Read() in any case before this line:
return new ScriptedMetricAggregate { _Value = scriptedMetric };

So reader state stays correct after current aggregate processing

[Mpdreamz]

Thank you for this @konbur 👍 Can you verify you have signed our CLA?

Are you able to attach a test for this?

For 6.0 we will rely on a new feauture in elasticsearch called typed_keys which will return aggregation names prefixed with type# which will completely replace the current heuristics based parser 🎉 🎈

[konbur]

CLA signed for now

Addition test (ScriptedMetricMultiAggregationTests) attached, integration mode required:

ScriptedMetricAggregationUsageTests.zip

[Mpdreamz]

Manually pulled this as per #2761 @konbur

Many thanks for the PR!