Limit number of lost particles written to disk.

[ebknudsen]

Description

This PR adds an option to limit the number of lost particles written to disk. This can be useful in the admittedly rare corner case when debugging leaky geometry models, to avoid being overwhelmed by the sheer number of files.

No regression test has been added - I simply don't know how to reliably generate a simple leaky geometry.

Fixes # (issue)
No present issue

Checklist

• [ x] I have performed a self-review of my own code
• [ x] I have run clang-format on any C++ source files (if applicable)
• [ x] 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)

[ebknudsen]

I've now added a regression test - based on the procedure of particle_restart_eigval, which seems stable enough

[paulromano]

@ebknudsen I've made some updates here on your branch:

• I've changed the default limit to -1, which means that if a user sets it to 0, it will completely disable the writing of lost particle files (seemed like that might be a desirable option for some).
• Fixed up associated documentation
• Refactored the test you had into a smaller "unit test" (for this case, we really don't care about the result, only that the correct number of lost particle files was created).

Since this was a little bit of a heavy-handed approach of making changes rather than suggestions, let me know if it looks OK to you; happy to iterate further if needed!

[ebknudsen]

@paulromano Cool. All fine by me. I agree on all your edits and btw. I have absolutely no problem with the direct edits :-).