This follows up to D104665 (which added umulo handling alongside the existing uaddo case), and generalizes for the remaining overflow intrinsics.
I went to add analogous handling to LVI, and discovered that LVI already had a more general implementation. Instead, we can port was LVI does to instcombine. (For context, LVI uses makeExactNoWrapRegion to constrain the value 'x' in blocks reached after a branch on the condition `op.with.overflow(x, C).overflow`.)
Differential Revision: https://reviews.llvm.org/D104932
For each of the x.with.overflow variants, if only the overflow bit is consumed, we can generate a direct overflow comparison. This precommits tests for each of the variants and tries to cover interesting cornercases.
