Add setting to optionally disable atomic relaxation

[amandalund]

Description

This adds a setting that allows users to optionally disable atomic relaxation in photon transport simulations. Atomic relaxation models the cascade of X-ray fluorescence photons and Auger electrons emitted when an inner-shell vacancy is filled. This option will be useful for performance benchmarking, and disabling relaxation may improve performance in simulations where detailed modeling of the secondary particle cascade is not needed.

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)

[paulromano]

Thanks @amandalund! Can you add a simple regression test to cover this case? Other than that, one comment on the documentation below:

[paulromano]

👍