Improve handling of google-protobuf not being loaded when profiler starts

[ivoanjo]

Current behaviour

In #1552 we added some code to improve the error message around an issue that a customer found but that we could not reproduce at the time.

In #1552 (comment) we finally got an example of how and why the issue triggers.

Expected behaviour

We should provide a good error message explaining what happened and how to fix it, rather than the vague "please report this message".

Steps to reproduce

See #1552 (comment) .

[ivoanjo]

Update on this one: With the migration to the new Ruby CPU Profiling 2.0, we don't need google-protobuf anymore. Thus, I don't think it's worth touching the loading code, as we plan on removing it soon.