DistributionMultiTable Enhancment for CDF Sampling

[melekderman]

This pull request introduces support for a new "direct-CDF" sampling mode for electron data, particularly data written from ACE files, in addition to the existing PDF-based mode. It updates the DistributionMultiTable class and its consumers to handle both modes, and modifies the sampling logic to correctly process direct-CDF tables. The changes are primarily focused on improving compatibility and accuracy for electron-related data structures and sampling routines.

Support for direct-CDF mode in distribution handling and sampling:

• Updated the DistributionMultiTable class to accept either a PDF (default) or a CDF directly, enabling "direct-CDF" mode for electron data. When a CDF is provided, the PDF is set to an empty array and the CDF is used as-is.
• Modified the from_h5_group method in electron_reaction.py to detect and use the direct-CDF mode when a "CDF" entry is present in the HDF5 group, both for secondary electron energy distributions and scattering cosine distributions. [1] [2]

Sampling logic enhancements:

• Refactored the _sample_multi_table function to support both direct-CDF and PDF-based sampling. The function now checks if the PDF is empty (direct-CDF mode) and performs linear interpolation between values using the CDF, or uses the existing PDF-based sampling logic otherwise. Special handling for degenerate tables (single value) is also added.## Summary of changes

Types of changes

• New feature (non-breaking change which adds functionality)

Associated Issues and PRs

• closes #
• related to Refactored Version of Electron Transport Capability #387

Associated Developers

• Dev: @ilhamv