Using streaming RPC to query ingesters doesn't support mixed chunks/blocks mode

When using `-querier.ingester-streaming=true` (which is now default), querier doesn't properly merge results from Chunks and Blocks-based ingesters, and only uses results from blocks-ingesters.

This is a problem during zero-downtime migration between the two modes.

Workaround is to disable `-querier.ingester-streaming`, then results are merged properly.