[cmd/golden] allow to group and accumulate data before comparing it

[atoulme]

Component(s)

cmd/golden

Describe the issue you're reporting

The golden binary tests whatever data is sent to it. Sometimes you want to check a whole collection interval, but that means you need to buffer the data for a duration.

Right now the workaround is to place a collector in front with a batchprocessor and a groupsbyattr processor to rearrange the data. Ideally, this should all be managed by golden.

[github-actions]

Pinging code owners:

• cmd/golden: @atoulme

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[axw]

Issue created by code owner, removing needs-triage.