This change should make it less confusing where utility code comes from.
Having it in two places made sense when we were debating whether to publish
Sandbox2 separately, but not any longer.
Follow-up changes will move `sandbox2/util.h` and rename the remaining
`sandbox2/util` folder.
PiperOrigin-RevId: 351601640
Change-Id: I6256845261f610e590c25e2c59851cc51da2d778
These where inadvertently introduced in an internal cleanup change.
This change also removes a C++17-ism in var_proto.h. To make things easier for
downstream projects, we should stick to C++11 for the time being.
PiperOrigin-RevId: 271117700
Change-Id: I4eaacec88be16e1a561d3f77a61acce0a1af0b9d
