Add the ability to tally microscopic cross sections in void materials

[GuySten]

Description

This PR add the ability to tally microscopic cross sections in void materials.

Fixes #3412.

Checklist

• I have performed a self-review of my own code
• I have run clang-format (version 15) 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)

[lewisgross1296]

Just for my own curiosity, what is the application/use case of this?

[GuySten]

It lets you calculate reaction rates in void regions without touching the model.
For example it can be used for calculation of equivalent thermal neutron flux (equivalent with respect to some thermal microscopic cross section).