Use a single uint64 for cell counts (#2749)
Use a single uint64 for cell counts (#2749)

Previously we switched to a vector so we could avoid read-after-write
depedencies that limited vectorization. However the setting of the
vector to false ends up being more costly with large tiles and little
intersection than the having the read-after-write of a single uint64_t.
TileDB-Inc/TileDB,TileDB-Inc/TileDB,TileDB-Inc/TileDB,TileDB-Inc/TileDB