Migrate IPF code from caf.toolkit

[BenTaylor-TfN]

Describe Changes

Code being removed from caf.toolkit can be seen here: https://github.com/Transport-for-the-North/caf.toolkit/pull/105

Task Checklist

• [ ] Have unittests been added (testing individual functions and their edge cases)
• [ ] Have integration tests been added (if applicable, to test modules of functionality)
• [ ] Updated RELEASE.md to reflect changes in PR
• [ ] Have new dependencies been added?
  • [ ] Have they been added to either requirements.txt or requirements_dev.txt.
  • [ ] Have they been added to setup.cfg
• [ ] Update docs to reflect change
• [ ] Migrate relevant issues from CAF.Toolkit

Also fixes #26

[codecov[bot]]

Codecov Report

Attention: 18 lines in your changes are missing coverage. Please review.

Comparison is base (a03bda2) 81.38% compared to head (a5c7ded) 86.33%.

Files	Patch %	Lines
...c/caf/distribute/iterative_proportional_fitting.py	94.69%	13 Missing :warning:
src/caf/distribute/array_utils.py	95.65%	5 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #33 +/- ## ========================================== + Coverage 81.38% 86.33% +4.94% ========================================== Files 9 11 +2 Lines 634 995 +361 ========================================== + Hits 516 859 +343 - Misses 118 136 +18 ```

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