Reduce per-instruction overhead in interpreter loop by youknowone · Pull Request #7315 · RustPython/RustPython

* Reduce per-instruction overhead in interpreter loop

- Defer prev_line update to when tracing is active
- Inline skip_caches_if_fallthrough, compute cache_entries once per instruction

* Unmark test_pdb_set_trace EXPECTED_FAILURE

prev_line deferral fix corrects pdb line tracking, making
these doctests pass.