* impl
* stash
* clean up
* do not apply when HT is small
* make branch static
* also in merge
* do not hardcode look ahead value
* fix
* apply to methods with cheap key calculation
* more tests
* silence tidy
* fix build
* support HashMethodKeysFixed
* apply during merge only for cheap
* stash
* fixes
* rename method
* add feature flag
* cache prefetch threshold value
* fix
* fix
* Update HashMap.h
* fix typo
* 256KB as default l2 size
Co-authored-by: Alexey Milovidov <milovidov@clickhouse.com>
