[inductor] fix scatter fallback and fallback in deterministic mode (#98339)
Fixes https://github.com/pytorch/pytorch/issues/93537
add `ir.ScatterFallback` to handle the mutation correctly of scatter/scatter_reduce fallback, also handle the case that `src` is a scalar, and lastly fallback in deterministic mode.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/98339
Approved by: https://github.com/jansel
