[Telemetry Operator] Track buffer sizes per pipeline

[a-thaler]

Description With https://github.com/kyma-project/kyma/pull/14347 a sidecar got introduced which is tracking the filesystem buffer size and exporting it as a metric with a nice grafana visualization. However, the buffer size overall brings not much value for operations as every individual pipeline buffer size is relevant.

Criteria

• refactor the application to be multi-pipeline dimensional, so watching the buffer sub-folders and label the metric with subfolder name
• Adjust the grafana dashboard to show buffer sized per pipeline
• Have a constant limit per pipeline visualized