Feature: Add support to k6 tags besides the group

[jfcorb]

For query and queryAt it will ideal to have some tags that could allow to analyze our response time better:

• To allow to correlate http_req_duration with the loki_* metrics
• To allow to group response times in different groups (pandas group-by)\

This is already possible with the http req in k6:

  const res = http.get('http://httpbin.test.k6.io/', {
    tags: {
      my_tag: "I'm a tag",
    },
  });