Code update for vectorized interpolate cpu uint8 (#96847)
- code style update
- use idx_ptr_xmin/idx_ptr_size instead of bounds
- compute wt_max inside _compute_indices_weights_aa (no significant overhead)
- added comments and explanations
- renamed xmin/xmax into ids_min, ids_size
Pull Request resolved: https://github.com/pytorch/pytorch/pull/96847
Approved by: https://github.com/peterbell10, https://github.com/NicolasHug, https://github.com/lezcano
