ML4SCI/DeepLenseSim/Model-4 ImportError for CDM and ULDM with newer pyHalo versions

[Shrishagk]

While testing Model IV, I encountered ModuleNotFoundError and ImportError for CDM and ULDM imports. This appears to be due to API changes in newer versions of pyHalo. This issue tracks the implementation of version-agnostic factory imports to ensure compatibility.

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##Proposed Fix
Replace the original import code with a try and except code block

try:
    from pyHalo.preset_models import preset_model_from_name
    # Use the factory function to get ULDM
    ULDM = preset_model_from_name('ULDM')
except Exception as e:
    # If that also fails, we'll need to see the specific error
    print(f"Failed to load ULDM: {e}")
    raise

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Note:

1. I tested using the latest commits from Fix hardcoded absolute paths in simulation scripts mwt5345/DeepLenseSim#1 (PR branch), since the fixes are not merged into main yet.
2. Even after resolving imports, the scripts sim_cdm.py and sim_no_sub.py fail with a FileNotFoundError for Galaxy10_DECals.h5.