Add particle weighting setters and getters

[jcurtis2]

Particles are created with an unset weight group and weight class. This can create issues that will result in PartMC failures.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.81%. Comparing base (da95a8d) to head (a7912ba).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #460      +/-   ##
==========================================
+ Coverage   90.69%   90.81%   +0.11%     
==========================================
  Files          55       55              
  Lines        2537     2569      +32     
  Branches      144      144              
==========================================
+ Hits         2301     2333      +32     
  Misses        163      163              
  Partials       73       73              

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.