[X86] Custom type legalize (v2i32 (fp_to_uint v2f64))) without avx512vl by...

[X86] Custom type legalize (v2i32 (fp_to_uint v2f64))) without avx512vl by widening to v4i32 and v4f64 instead of v8i32 and v8f64. Make it aware of x86-experimental-vector-widening-legalization

We have isel patterns for v4i32/v4f64 that artificially widen to v8i32/v8f64 so just use that.

If x86-experimental-vector-widening-legalization is enabled, we don't need any custom legalization and can just return. I've modified the test RUN lines to cover this case.

llvm-svn: 341765