[llvm] [ObjCARC] Optimize MayAutorelease by skipping over pools (PR #188583)

[Akira Hatanaka via llvm-commits]

ahatanak wrote:

 I'm not sure why you didn't see a behavioral change on your end, but this is not NFC. With the test case I posted, the push/pop pair in `@caller` is preserved before this patch but eliminated after it. That's the expected result, but it is a functional change, so this PR needs a test case.

https://github.com/llvm/llvm-project/pull/188583