[flang] Replace Arithmetic Ops with their builtin conunterpart

Replaces `fir.add, fir.sub, fir.mul, fir.div` with their builtin
conuterparts.

This part of upstreaming effort, upstreams some parts of:
PR:https://github.com/flang-compiler/f18-llvm-project/pull/681

Reviewed By: schweitz

Differential Revision: https://reviews.llvm.org/D98719