Bytecode compatibility - Normalize Loop/Branch Jump Semantics

[youknowone]

Summary

Background:
There are many mismatches involving jumps and stack effects (e.g., LOAD_CONST/
JUMP_BACKWARD, JUMP_BACKWARD/JUMP_FORWARD, POP_TOP/CALL, POP_EXC/CALL patterns),
suggesting CPython/jump normalization drift.

Task:

• Audit RustPython compiler code generation for branch target calculation and jump
  lowering.
• Ensure jump target normalization matches CPython offset-to-index expectations in dis
  output.
• Verify POP_TOP/JUMP pairing and loop backedge generation around FOR_ITER/while/for
  comprehensions.
• Re-run comparisons focused on core modules and remove false positives caused by
  different normalization if safe.

Acceptance criteria:

• Diff counts for major jump-related pairs decrease substantially.
• Critical loop-heavy modules (html/entities.py, inspect.py) show improved
  instruction alignment.

Details

[youknowone]

RustPython#7580