Fix a bug in compton scattering shell selection

[GuySten]

Description

Currently, in compton scatter openmc select electron to interact with irrespectively of the incident photon energy. This PR change that to resample the shell until the incident photon energy is higher than the electron binding energy.

This PR also change the compton doppler broadening algorithm to better match https://serpent.vtt.fi/download/Kaltiaisenaho_MSc_2016.pdf.

Checklist

• I have performed a self-review of my own code
• I have run clang-format (version 18) on any C++ source files (if applicable)
• I have followed the style guidelines for Python source files (if applicable)
• I have made corresponding changes to the documentation (if applicable)
• I have added tests that prove my fix is effective or that my feature works (if applicable)