* test: add test for pp computation

* bench: add a digest computation bench

* refactor: Optimize digest computation and update tests

- Remove flate2 dependency from codebase
- Replace ZlibEncoder with bincode::serialize in compute_digest function
- Update test_pp_digest expected results to align with compute_digest changes

Bench results:
```
compute_digest          time:   [1.4451 s 1.4571 s 1.4689 s]
                        change: [-29.357% -27.854% -26.573%] (p = 0.00 < 0.05)
                        Performance has improved.
```