[llvm] [X86] lowerFPToIntToFP - handle UI2FP on AVX512VL targets and i64 types on AVX512DQ targets (PR #162656)

[Kavin Gnanapandithan via llvm-commits]

KavinTheG wrote:

Update:
- Rebased and squashed previous commits.
- Fixed label mismatches and unnecessary labels in `isint.ll`.
- Added i32 optimizations in addition to i64 handling. 

I understand your earlier feedback suggested focusing on i64 first, but I believe this commit doesn't introduce too much complexity. 


https://github.com/llvm/llvm-project/pull/162656