Fix a crash in :func:`os.spawnv` and :func:`os.spawnve` when an *argv*
item's :meth:`~os.PathLike.__fspath__` method mutates the *argv* list
during argument conversion.  :func:`!os.spawnv` argument conversion errors
other than :exc:`TypeError`, such as the :exc:`ValueError` for an embedded
null, are no longer replaced with a generic :exc:`TypeError`.
