util/AllocatedArray: migrate from {Const,Writable}Buffer to std::span
util/AllocatedArray: migrate from {Const,Writable}Buffer to std::span

CM4all/beng-proxy,CM4all/beng-proxy,CM4all/beng-proxy,CM4all/beng-proxy,CM4all/beng-proxy,CM4all/beng-proxy