V2: Ensure ingested data becomes deterministically even if there is no profile flow

[simonswine]

As part of extending the integration tests to cover V2 experimental storage, we noticed, after stopping ingestion all together, we are not able to deterministically query profiles.

As a workaround we keep pushing some extra profiles for another tenant before we querying them back.

https://github.com/grafana/pyroscope/pull/4185#discussion_r2082396157

[kolesnikovae]

I believe we should include the dataset index in segments: https://github.com/grafana/pyroscope-squad/issues/447 – this will address the issue