split predispatch pass into multiple passes (#121592)
Summary:
It's very difficult to debug the passes ineffectiveness, with them mingled in one single pass container. Here we extract them into seperate passes with diagnostics info.
This is also required for a later change, where we must run shape prop on each of these passes, in order for the subsequent passes to have the correct shape information.
Reviewed By: frank-wei
Differential Revision: D53579545
Pull Request resolved: https://github.com/pytorch/pytorch/pull/121592
Approved by: https://github.com/frank-wei
