Bytecode parity: align borrow optimization with CFG traversal by youknowone · Pull Request #7773 · RustPython/RustPython

- compile.rs: unwind_fblock_stack returns whether a finally ran so
  return-statement emission can adjust location handling; restructure
  try/except/finally cleanup to preserve or drop boundary NOPs based on
  whether the body falls through; rework f-string lowering with
  count/join helpers; remove the per-collection-type heuristic for
  AST-level folding and defer to flowgraph passes; add several folding
  helpers and a ComprehensionLoopControl enum.
- ir.rs: re-run unary/binop folding around tuple folding, add
  reorder_conditional_scope_exit_and_jump_back_blocks and several block
  classification helpers, add MAX_STR_SIZE, change is_exit_without_lineno
  to take the block list.
- symboltable.rs: in analyze_cells, remove names owned as cells in
  function-like scopes from the parent's free set; mark lambda scope
  type explicitly.