Introduce SubstituteLifetimes.
This method allows (constrained) manipulation of the lifetimes. It also has
well-defined (but not yet implemented) behaviour in the presence of HRTBs.
PiperOrigin-RevId: 440886942
Extremely experimental interop tooling for C++ and Rust.
Please don‘t use, this is an experiment and we don’t yet know where will it take us. There will be breaking changes without warning. Unfortunately, we can't take contributions at this point.