Investigation about async-hooks

In a script of mine, where I heavily use use callbacks, seems to get an extremely high spike of calls of the function `destroy` in the `async-hooks` file. https://github.com/elastic/apm-agent-nodejs/blob/master/lib/instrumentation/async-hooks.js#L103

All the green spans are for `internal/async_hooks.js`, and the blue below is the mentioned `destroy` function.

For me it's now a question if we should not remove this async monitoring all together. It uses a lot of computation power which could be used for the actual task.