Fix GH-22256: Preserve frameless argument order

[prateekbhujel]

Frameless calls keep CV arguments in their original slots until the handler runs. If a later argument changes one of those CVs, the handler sees the new value instead of the value from when the earlier argument was evaluated.

Copy earlier CV arguments before compiling a later expression that may have side effects. The common variable, literal, and constant argument paths remain unchanged.

This happens before the frameless opcode runs, so the __toString() re-entry protection proposed in #21815 does not cover it.

Includes tests for assignment, increment, and mutation through a nested call.

Fixes GH-22256