Collect usage statistics around executor being used
When a runner is registered (at least) or ideally when it contacts GitLab (thus getting data in retrospect) it should send data back so that GitLab or the Runner can report back usage statistics. Ideally, this would include a lot of things, but if it's easier to start with one thing, let's make it the Executor.
Since in &535 (closed) we added support for a new (and possibly the last bespoke) executor, this is a great time to start tracking these statistics to understand how users are using the runner.