[llvm] [ADT] Add standalone_debug attribute to SmallVectorBase (PR #82527)

[Reid Kleckner via llvm-commits]

rnk wrote:

In the case of libc++, this annotation was required because these `__hash_node` structs have constructors, but they are never called, and the struct lifetime is managed implicitly with reinterpret_cast. I don't think that's the case here.

https://github.com/llvm/llvm-project/pull/82527