Added the option for an initial individual

[jmafoster1]

Summary

Added the ability to specify an initial individual for HillClimberDiscovery, e.g. from a different causal discovery technique. I also moved max_iterations into the function arguments rather than the class object.

Checklist

Before you mark your PR as ready for review, please ensure you have completed the following.

• Added unit tests for new functionality
• Properly documented any new code
• Updated Sphinx documentation in docs/ and checked for updated configuration/runtime options
• Added a jupyter notebook tutorial in docs/source/tutorials for any new functionality
• Verified local docs build with sphinx-build -W source/ build

[github-actions]

🦙 MegaLinter status: ⚠️ WARNING

Descriptor	Linter	Files	Fixed	Errors	Elapsed time
⚠️ PYTHON	black	32		1	0.74s
✅ PYTHON	pylint	32		0	4.7s

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.26%. Comparing base (1c8eaf1) to head (78e0c66).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #408      +/-   ##
==========================================
- Coverage   98.57%   98.26%   -0.32%     
==========================================
  Files          26       26              
  Lines        1615     1612       -3     
==========================================
- Hits         1592     1584       -8     
- Misses         23       28       +5     

Files with missing lines	Coverage Δ
causal_testing/discovery/hill_climber_discovery.py	90.19% <100.00%> (-9.81%)	⬇️

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[jmafoster1]

So we were at 110% coverage before??

[jwhogg]

lgtm