[compiler-rt] [scudo] Add missing thread-safety analysis annotations. (PR #68072)

[Clement Courbet via llvm-commits]

legrosbuffle wrote:

> One quick question, why do we need to annotate `REQUIRES` capability here if we already mark it as `ASSERT_CAPABILITY`?
> 
> https://clang.llvm.org/docs/ThreadSafetyAnalysis.html#assert-capability-and-assert-shared-capability

My understanding is that `ASSERT_CAPABILITY` is a purely dynamic check, and does not imply `REQUIRES`. Adding @aaronpuchert for confirmation.

https://github.com/llvm/llvm-project/pull/68072