[v2] Rename "metric" entity to "metricset"

[axw]

The metrics API defines a metric entity, which is really a set of metrics. I propose that we rename this to "metricset", or something similar. Calling it "metric" might give the impression that it is a singular measurement.

[watson]

How about just metrics (plural). I try to stick to one-word names if I can in these cases. But maybe I misunderstood the use-case here...

[axw]

This is for v2 objects, e.g.

{"metadata":{}}
{"transaction":{}}
{"metrics":{"tags":{}, "samples":{}}}

"metrics" as an object name seems a bit odd to me, but better than just "metric". We could flatten the structure so we fold "tags" into each entry of "samples", but that would lead to a lot of repetition.

[roncohen]

I like metricset

[watson]

I'm fine either way. Just wanted to throw in the other option 😃

[roncohen]

metricbeat uses 'metricset' as well by the way: https://www.elastic.co/guide/en/beats/metricbeat/current/metricbeat-modules.html