[clang] Diagnose problematic uses of constructor/destructor attribute (PR #67360)

[Aaron Ballman via cfe-commits]

AaronBallman wrote:

> I think we're going to be stuck with 'warning-as-default-error' here, and let compiler-rt and tests/etc opt-out. I realize that makes the error not as effective, but it is really the one 'good' way for the 'implementation' in this case to handle itself.

Yeah, having slept on it, I think I agree that warning-defaults-to-error is probably the best we can do here. I think I will treat `init_priority` the same way so all three attributes have consistent priority handling.

https://github.com/llvm/llvm-project/pull/67360