Cleanup tasks for v1.0

[sethrj]

• [ ] Standardize nomenclature: #721
• [ ] Reorganize files
  • [x] params/helper/distribution for celeritas/random? see #1356
• [ ] Revisit namespaces (setup vs runtime?)
• [ ] Move stream operators alongside the classes (e.g., merge ArrayIO.hh into Array.hh) now that we're no longer worried about propagating headers into CUDA/HIP
• [ ] Replace lock_guard with scoped_lock
• [ ] Add numeric separators 1'234'567 where it's clean/meaningful to do so?
• [ ] Upgrade Span with CTAD and smarter constructors to eliminate make_span?
• [x] Trapezoid integrator (#1537 )
• [ ] CDF sampler
• [ ] Use C indexing for cyl field
• [ ] use std::filesystem
• [ ] ArrayUtils has a few Real3-specific/geometric utils (e.g. cross product), but sampling methods are in geocel: just move real3 and isotropic distribution to corecel
• [ ] GeantGeoTrackView in single precision loses accuracy from convert_from_geant but maybe it doesn't matter