[clang] Introduce paged vector (PR #66430)

[Jakub Kuderski via cfe-commits]

kuhar wrote:

@vgvassilev 
> I find the use of the macro I proposed cleaner though.

Ideally, I think we could have an llvm-specific macro that combines the guard and the check (say `LLVM_EXPECT_DEATH`), so that it's less of a footgun. In any case, the failures should be resolved now, and we can iterate it further in the future.

https://github.com/llvm/llvm-project/pull/66430