[clang] [clang][CGRecordLayout] Remove dependency on isZeroSize (PR #96422)

[Michael Buch via cfe-commits]

Michael137 wrote:

> For CGExprConstant, the code is checking "empty" in the sense of whether there's a corresponding LLVM field. So almost certainly needs changes. Not sure how that isn't causing test failures; maybe there's missing test coverage.

Yea I was pretty sure we'd have to adjust that too. Will try to get some coverage here

https://github.com/llvm/llvm-project/pull/96422