* use mmap bitslice and a metadata file to avoid loading
* fix and test reported files
* add new files to flusher
* update rocksdb+blob_store compatibility test
* switch to DynamicMmapFlags
* fix setting deleted to `false` on short bitslice
* remove `MmapBitSlice::extend`
* add some more tests to mmap sparse vector storage
* calculate deleted_count and next_point_offset on load
* get rid of metadata file
* cleanup
* fix test
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Co-authored-by: generall <andrey@vasnetsov.com>