[CIR] Upstream handling for overflow builtins

[andykaylor]

Overview

Upstream handling for the __builtin_add_overflow, __builtin_sub_overflow, and __builtin_mul_overflow functions, including implemetation and lowering of the cir.binop.overflow operation and the related variations of these builtins.

Suggested minimal test case

bool test_add_overflow_uint_uint_uint(unsigned x, unsigned y, unsigned *res) {
  return __builtin_add_overflow(x, y, res);
}

Existing incubator tests

clang/test/CIR/CodeGen/builtins-overflow.cpp

[siddu0660]

We would like to work on this

[adams381]

I put the pull request out for review.