[clang] [clang] handle fp options in __builtin_convertvector (PR #125522)

[Shafik Yaghmour via cfe-commits]

https://github.com/shafik commented:

Can we also add a summary, explaining your implementation e.g. "added TrailingObjects to `ConvertVectorExpr` containing ...." 

https://github.com/llvm/llvm-project/pull/125522