Fixing  compute_results_count_sparse_string for multiple range threads.
Fixing  compute_results_count_sparse_string for multiple range threads.

This fixes an incorrect computation for a partition size in
compute_results_count_sparse_string when there are multiple range
threads (result tiles < num cores). The number of cells of the tile was
used when the max_cell index for this call should have been used.

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TYPE: IMPROVEMENT
DESC: Fixing compute_results_count_sparse_string for multiple range threads.

TileDB-Inc/TileDB,TileDB-Inc/TileDB,TileDB-Inc/TileDB,TileDB-Inc/TileDB