Update repo to require CMake 3.16

[traversaro]

We have been requiring the use of CMake 3.16 for robotology repos since September 2020 (see robotology/robotology-superbuild#462). Now it could be a good time to review this repo and requiring CMake 3.16 also here, as these will drastically simplify some boilerplate.

[traversaro]

The first step after that is to finally accept #50 .

[traversaro]

At this point, we could directly target CMake 3.23, so we can also switch to use FILE_SET HEADERS to install headers, as Ubuntu 24.04 apt has a newer CMake, and Ubuntu 22.04 users can install a recent cmake with kitware's repo.