[llvm] [ArrayRef] Add constructor from iterator_range<U*> (NFC). (PR #137796)

[David Blaikie via llvm-commits]

dwblaikie wrote:

(seems about right to me, I'll leave it to @artagnon for the final approval, unless something contentious comes up (if so, do tag me/reach out, happy to weigh in/help resolve))

https://github.com/llvm/llvm-project/pull/137796