Unbind Cat pattern (#101767)
In continuation to previous diffs, this diff merges unbind->cat / unbind-> stack pattern.
In combination with previous diffs, this can handle split->squeeze->[cat/stack]
Since many of the cases are similar to split->cat, we reuse SplitCatSimplifier
Differential Revision: [D45955486](https://our.internmc.facebook.com/intern/diff/D45955486/)
Pull Request resolved: https://github.com/pytorch/pytorch/pull/101767
Approved by: https://github.com/jansel
