* Add cache to block window
* Copy the window heap slice with the right capacity
* Use WindowHeapSliceStore
* Use the selected parent window as a basis (and some comments and variable renames)
* Clone slice on newSizedUpHeapFromSlice
* Rename isNotFoundError->currentIsNonTrustedBlock
* Increase windowHeapSliceStore cache size to 2000 and some cosmetic changes
