spirv-fuzz: Add IdIsIrrelevant fact ids introduced during module donation

When one module is donated to another, we can add the "IdIsIrrelevant" fact to all of the ids that correspond to instructions from the donor module. We should do this whether functions are being donated in a livesafe manner or not. However, we should *not* add this fact for additional instructions that are used to make a function live-safe, such as instructions that manipulate the loop limiter.