[Bug] Protobuf integration in examples

[yellowhatter]

Describe the bug

Protobuf keeps breaking CMake scripts from time to time. Need to figure out more or less stable approach to integrate it. Maybe conan? Or build it's exact version from source in the example directory?

To reproduce

System info

[cvilas]

The right approach might be to eliminate protobuf from this repository completely. After all it is a third-party dependency Zenoh developers have no control over. Since Zenoh just transports bytes and is independent of any serialisation framework, why even carry the burden, and make undesirable compromises to make it work? Protobuf adds little to no value in this repo itself. Leave it to the user to integrate it into their application as they please.

Please don't force a package manager on us users though. CMake is good and has to work.