fix: validation for empty groups should fail job

fix: validation for empty groups should fail job

Noticed this when merging !6874 (merged), we meant to prevent this from happening in !6859 (merged) but missed a spot in the script.

We need this fixed to deploy the recording rules for all aggregation sets to mimir.

chore: remove empty rule groups in mimir

This removes the empty rule groups from mimir aggregation sets

chore: remove existing empty rule files

This removes existing empty rule files from Prometheus and Thanos. We didn't care about these files for deployment, but it's easier to fix this way rather than running different validation scripts for Mimir vs Thanos & Prometheus.