Explanation: One of the initializers were missing and the other was crashing at
runtime due to a faulty signature in the overlay.
Issue: rdar://149846666
Risk: Low, the fix is additive.
Testing: Regression test added.
Original PR: #81097
Reviewer:
A first step towards creating safe overloads for C++ APIs using span
(rdar://139074571).
Note that we need to mark span as owned because it the libc++
implementation was mistakenly recognized as owned and might now rely on
span methods like `data` being renamed as `__dataUnsafe`. We will change
it under a new interop version. But for the time being, we want
consistent behavior across stdlib versions.
