[llvm] [X86] Remove def32 and drop redundant zero extensions after `isel` (PR #225462)

[Akash Manna via llvm-commits]

akash-manna-sky wrote:

I know there are conflicts, basically they are from my own PR https://github.com/llvm/llvm-project/pull/223750 , I will fix those after your suggestions. 

https://github.com/llvm/llvm-project/pull/225462