Snapshot::build_from add test to calculate overhead for listing only newer versions

[gotocoding-DB]

TEST 1: Building snapshot WITHOUT checkpoint
========================================
Building snapshot at version 100000 (no checkpoints)...

Measuring memory usage...

=== Snapshot Memory Usage (NO CHECKPOINT) ===
Versions: 0-100000 (100001 commits)
Checkpoints: 0

Memory Breakdown:
  Stack memory:        3048 bytes (    2.98 KB)
  Heap memory:     35577593 bytes (34743.74 KB)
  Total memory:    35580641 bytes (34746.72 KB, 33.93 MB)

Per-commit average: 355.8 bytes

========================================
TEST 2: Creating checkpoint and rebuilding snapshot
========================================
Creating checkpoint at version 99800...
Building snapshot at version 100000 (with checkpoint at 99800)...

Measuring memory usage...

=== Snapshot Memory Usage (WITH CHECKPOINT) ===
Versions: 0-100000 (100001 total)
Checkpoint at: 99800
Commits in memory: 200 (versions 99801-100000)

Memory Breakdown:
  Stack memory:        3048 bytes (    2.98 KB)
  Heap memory:     23102800 bytes (22561.33 KB)
  Total memory:    23105848 bytes (22564.30 KB, 22.04 MB)

Per-commit average: 115529.2 bytes

========================================
COMPARISON
========================================
Memory saved by checkpoint: 12474793 bytes (12182.42 KB, 11.90 MB)
Commits saved from memory: 99801 commits
Memory reduction: 35.1%
test snapshot::tests::test_snapshot_memory_usage ... ok