feat: Parameterize mean excitation energy in Material

[andiwand]

Since this came up in a few discussions I propose to add the mean excitation energy as a configurable parameter to Material. This parameter allows for more accurate modeling of the ionization energy loss for low momentum particles.

This is implemented in a way that users can specify it but do not have to. If they don't we default to the original approximation.

[codecov]

Codecov Report

Attention: Patch coverage is 75.00000% with 4 lines in your changes are missing coverage. Please review.

Project coverage is 48.92%. Comparing base (4c0925e) to head (60e147e).
Report is 78 commits behind head on main.

Files	Patch %	Lines
Core/src/Material/Material.cpp	73.33%	2 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2892      +/-   ##
==========================================
+ Coverage   48.91%   48.92%   +0.01%     
==========================================
  Files         494      494              
  Lines       28834    28845      +11     
  Branches    13671    13670       -1     
==========================================
+ Hits        14104    14113       +9     
- Misses       4874     4876       +2     
  Partials     9856     9856              

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