[compiler-rt] [scudo] Make BufferPool typed and always express sizes in terms of element count (PR #66896)

[Mitch Phillips via llvm-commits]

hctim wrote:

Looks reasonable to me, two things:

1. Seems unnecessary to template the `uptr` type of the buffer class, unless you can elaborate on why you need that?
2. Can you please add a small justification in your commit message about how you discovered the mismatch? It's nice to know the backstory here.

https://github.com/llvm/llvm-project/pull/66896