[llvm] [memprof] Use std::vector<Frame> instead of llvm::SmallVector<Frame> (NFC) (PR #94432)

[Kazu Hirata via llvm-commits]

kazutakahirata wrote:

> My recollection was that even `SmallVector<T, 0>` had some advantages over std::vector ( https://llvm.org/docs/ProgrammersManual.html#llvm-adt-smallvector-h mentions some possible reasons for that) - so maybe worth using that instead?

I've tried `SmallVector<T, 0>`, but that didn't improve the performance.  Now, my `llvm-profdata` is not built with FDO+ThinLTO, so there may be some missed inlining opportunities or something that would make `SmallVector<T, 0>` a better choice than `std::vector<T>` here.

https://github.com/llvm/llvm-project/pull/94432