[clang] [ObjC] Check entire chain of superclasses to see if class layout is statically known (PR #81335)

[Zhaoxuan Jiang via cfe-commits]

nocchijiang wrote:

@AZero13 Do you have any news or plans regarding LTO support? We have several projects with substantial existing Objective-C code, and the performance benefits of LTO support could be significant. I would be interested in taking on a portion or the entirety of this work if it is not currently on your priority list.

https://github.com/llvm/llvm-project/pull/81335