We currently have a workaround for MSVC, which has constexpr pointer arithmetic bugs. The bug seems to still exist and the existing code for non-MSVC compilers doesn't build.

This alternative constexpr constructor avoids pointer arithmetic and seems to be working for all, including MSVC.

PiperOrigin-RevId: 592586957
Change-Id: Ic585693c3a7abaab5fbbc0954b8ee924994f8dbf