=== pyroscope-0001: PhlareDB.GetBlockStats O(B*U) -> O(B+U) ===

               scale    defective      fixed    speedup
-------------------------------------------------------
  B=  500 U= 100       1.81ms     0.04ms     47.0x
  B= 1000 U= 200       7.59ms     0.08ms     96.3x
  B= 2000 U= 200      15.66ms     0.15ms    103.0x
  B= 2000 U= 500      38.00ms     0.17ms    224.5x
  B= 5000 U= 500     102.96ms     0.36ms    282.2x
  B=10000 U=1000     239.79ms     0.55ms    438.8x

Conclusion: O(B*U) -> O(B+U) — set hoist on the requested ULID list.
At B=10k U=1k (long-retention pyroscope tenant), speedup is 100x+.
