depend on string_view without depending on all of
//absl/strings:strings

New code that uses string_view.h should depend on
//absl/strings:string_view (Bazel) or
absl::string_view (CMake) instead.
PiperOrigin-RevId: 547283268
Change-Id: I6006b19605ce377d12c462129dda14251d16e1c1