Fix XLA symbolic shapes binding (#88928)
Obsoletes https://github.com/pytorch/pytorch/pull/88772
Mostly revolves around NOT assuming that the inside is a SymNode,
but instead duck-typed to be a SymNode.
Signed-off-by: Edward Z. Yang <ezyang@fb.com>
Pull Request resolved: https://github.com/pytorch/pytorch/pull/88928
Approved by: https://github.com/SherlockNoMad
