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

[Aaron Ballman via cfe-commits]

AaronBallman wrote:

> > runtime, whereas a `consteval` one cannot. WDYT?
> 
> This makes sense to me. Also, see my comment on #67376. It looks like someone else is messing with this area as well, and are editing things in an incompatible way, so we should make sure that these don't conflict.

Good catch -- I think it would make sense to land these changes here first and then rebase on top of it, because this is generalizing the existing code in a way that should make it slightly easier to handle template instantiations (and hopefully handle them for `constructor`, `destructor`, and `init_priority` at the same time).

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