feat: clarify FhirData setter behavior with explicit replace parameter

[skalwaghe-56]

Description

Clarifies the behavior of resource list setters in the FhirData class by adding explicit control over whether they add to or replace existing resources.

Related Issue

Closes #123 - Clarify Resource List Setter Behavior in FhirData

Changes Made

• Modified problem_list, medication_list, and allergy_list setters in FhirData class to accept explicit replace parameter
• Added dict-based interface for replace control: {'resources': [...], 'replace': True}
• Maintained backward compatibility - existing list assignments default to add behavior
• Updated documentation for all three setters with clear examples and parameter descriptions

Testing

• All existing tests pass (475/475) confirming backward compatibility
• No breaking changes introduced
• Existing functionality preserved while adding new explicit control

Checklist

• I have read the contributing guidelines
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

Additional Notes

The implementation uses a dict-based approach for the replace parameter since Python property setters can only accept a single value argument. This provides explicit control while maintaining full backward compatibility with existing code.