srSILO: make `Merge` Step in `Read Sorting` More Expressive

[gordonkoehn]

In the pro-processing of srSILO there the sorting rust utilities are at times not very expressive in logs, especially the Merge step could have some more logs:

noble-amd64-base wisepulse-pipeline[990482]:   sampleId-H1_25_2025_08_30.ndjson.zst
Oct 03 13:04:32 Ubuntu-2404-noble-amd64-base wisepulse-pipeline[990482]:   sampleId-F2_05_2025_07_11.ndjson.zst
Oct 03 13:05:43 Ubuntu-2404-noble-amd64-base wisepulse-pipeline[990477]: ✓ Created 160 chunks
Oct 03 13:05:43 Ubuntu-2404-noble-amd64-base wisepulse-pipeline[990474]: mkdir -p tmp
Oct 03 13:05:43 Ubuntu-2404-noble-amd64-base wisepulse-pipeline[1044173]: === Merging sorted chunks ===
Oct 03 13:05:43 Ubuntu-2404-noble-amd64-base wisepulse-pipeline[1044174]: Merging 160 chunks...

No Logs for 20min + here