[Enhancement] Iterators must optionally contribute to the block cache.

[koculu]

After implementing block pinning in PR #64, the blocks read by iterators are no longer tracked in the block cache. This change optimizes both memory usage and performance, particularly during the compaction stage, which heavily relies on iterators.

It would be beneficial to add an option to the iterator creation method, allowing consumers to decide whether the iterator's scan should contribute to the block cache or not.