[llvm] [GlobalISel] Combiner: Install Observer into MachineFunction (PR #102156)

[Tobias Stadler via llvm-commits]

tobias-stadler wrote:

> We're also using this in the IRTranslator. Do those need changing at all?

Good catch.  I have put up #102379. Those were the last improper uses of RAIIDelegateInstaller.

https://github.com/llvm/llvm-project/pull/102156