Background

We decided to close SERVER-106617 as "Works as Designed", keeping the bucketsNs field in the output of $collStats. A TODO was left in the test code to review whether checking for bucketsNs consistency should be re-enabled for viewless timeseries.

Changes

Since bucketsNs is kept in the $collStats output (to avoid a backward-incompatible change in 9.0), we unconditionally check that all shards report the same bucketsNs value, removing the viewless timeseries conditional. The check now also includes a detailed error message to help diagnose discrepancies.