45 parallelize point est hist and naive stack

Problem & Solution Description (including issue #)

This PR parallelizes naive stack. It modifies some of the logic from input_iterator and adds functions to data.py in order to be able to use the iterator to qp ensambles.

Code Quality

[ ] My code follows the code style of this project
[ ] I have written unit tests or justified all instances of #pragma: no cover; in the case of a bugfix, a new test that breaks as a result of the bug has been added
[ ] My code contains relevant comments and necessary documentation for future maintainers; the change is reflected in applicable demos/tutorials (with output cleared!) and added/updated docstrings use the NumPy docstring format
[ ] Any breaking changes, described above, are accompanied by backwards compatibility and deprecation warnings

Codecov Report

Attention: 4 lines in your changes are missing coverage. Please review.

Comparison is base (da3a845) 97.13% compared to head (0f62392) 96.95%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #64 +/- ## ========================================== - Coverage 97.13% 96.95% -0.18% ========================================== Files 32 32 Lines 1675 1709 +34 ========================================== + Hits 1627 1657 +30 - Misses 48 52 +4 ``` | [Files](https://app.codecov.io/gh/LSSTDESC/rail_base/pull/64?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=LSSTDESC) | Coverage Δ | | |---|---|---| | [src/rail/core/stage.py](https://app.codecov.io/gh/LSSTDESC/rail_base/pull/64?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=LSSTDESC#diff-c3JjL3JhaWwvY29yZS9zdGFnZS5weQ==) | `99.14% <100.00%> (+0.03%)` | :arrow_up: | | [src/rail/core/data.py](https://app.codecov.io/gh/LSSTDESC/rail_base/pull/64?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=LSSTDESC#diff-c3JjL3JhaWwvY29yZS9kYXRhLnB5) | `99.23% <88.88%> (-0.37%)` | :arrow_down: | | [src/rail/estimation/algos/naive\_stack.py](https://app.codecov.io/gh/LSSTDESC/rail_base/pull/64?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=LSSTDESC#diff-c3JjL3JhaWwvZXN0aW1hdGlvbi9hbGdvcy9uYWl2ZV9zdGFjay5weQ==) | `94.73% <90.62%> (-5.27%)` | :arrow_down: |

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LSSTDESC / rail_base