Implementation of forced collision variance reduction scheme

[GuySten]

Description

This PR implements forced collision variance reduction scheme.
Forced collision is useful for problems when we specificaly need collision estimator in optically thin cells.
IMO the most useful example is calculation of heating in a thin layer of material.

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)

[GuySten]

This PR should wait for #3849