Index generation improvements

[delucchi-cmu]

Change Description

Closes #206.

• Performs the index de-duplication when reading from the original leaf file.
• Pass the dask client and use explicitly for the compute call.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 99.75%. Comparing base (c5af8dd) to head (4c58d76). Report is 2 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #248 +/- ## ======================================= Coverage 99.75% 99.75% ======================================= Files 24 24 Lines 1204 1204 ======================================= Hits 1201 1201 Misses 3 3 ```

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