Allow taking more metrics than just the first one from Prometheus response
Currently, we only take the first "metric" from a Prometheus response. That means, every row in a response has the same labels
column. Optionally, we want to support multiple metrics, leading to a response such as:
"{consumergroup=shufflebench-kstreams, partition=0, topic=input}",1702453530,2774
"{consumergroup=shufflebench-kstreams, partition=0, topic=input}",1702453531,2995
"{consumergroup=shufflebench-kstreams, partition=1, topic=input}",1702453530,2774
"{consumergroup=shufflebench-kstreams, partition=1, topic=input}",1702453531,2995