One `Scope` in POTel-Base

[szokeasaurusrex]

The potel-base branch currently defines two scope classes: Scope and PotelScope. @antonpirker says this is because we might add an "errors only" distribution, which would need the non-potel Scope.

However, until we decide to do this, it would be simpler to just expose a single Scope type. We can always later split the types if we decide we need the errors-only distribution.