The tutorials and example code are inconsistent w.r.t. versioning.

Tutorials start in the versioned docs set. https://docs.bazel.build/versions/4.0.0/tutorial/cpp.html
But the examples they point to are in https://github.com/bazelbuild/examples, and not versioned.

This means that as Bazel evolves, the examples should change too. But then, the tutorials for older LTS versions of Bazel might point to broken examples.

A better situation would be for the tutorial pages to live in the examples repository, and only have links from the main bazel docs into the examples repo.

We can reorg the example tree so there is a top root that specifies bazel track (2, 3, 4, ...). At the beginning of a new LTS cycle we copy the most recent tree to the new one and tweak as appropriate.