Provide endpoint to get measurement counts from core

[dominikriemer]

Body

In the configuration view, the counts of data lake measurements are fetched asynchronously for all data lake measures. In deployments with many different measurements, many queries are sent from the UI to the core, leading to slow response times.

We should add a new endpoint to the core which allows to receive the count values for measurements all at once.

StreamPipes Committer

I acknowledge that I am a maintainer/committer of the Apache StreamPipes project.