Tianqi Chen
45e1b8233a
Refactor Tensor arithmetic dispatch away from tirx.generic (#19943)
## Summary
- Move whole-Tensor arithmetic and cast dispatch onto `te.Tensor` while
scalar TIRx smart constructors decline whole-Tensor operands.
- Remove the legacy `tirx.generic` module, TOPI import-time mutation
bridge, and obsolete aliases.
- Migrate scan and cast callers while preserving identity-gated Thrust
sum selection.
Whole-Tensor behavior now lives with TE, leaving scalar TIRx
construction independent of TOPI initialization.