Structured mesh TLE when delta tracking #3902
Description
Adding features to allow for a track length estimator when delta tracking and tallying integral flux to a structured mesh. Previous implementation: https://www.tandfonline.com/doi/full/10.1080/23324309.2026.2618791.
This would also be useful when hybrid surface-delta tracking so that we can tally to the same mesh in the same way to all regions in the problem, like what's proposed in #3343. Working with @pshriwise on Delta tracking project with @apingegno, @willzywiec, and myself using work done in #3343 and associated issues.