Cron: Add support for parsing Luxon zones

### Problem Statement

The [cron](https://github.com/kelektiv/node-cron) package uses Luxon for time zones. This allows us to specify `system` to use the system timezone for example. Information about this can be found here: https://github.com/moment/luxon/blob/master/docs/zones.md#specifying-a-zone

However, the problem that currently stands is that these zones aren't supported and thus cause Sentry to show an invalid monitor configuration error for new cron jobs.


### Solution Brainstorm

I believe that Sentry should parse Luxon zones in the automatic cron instrumentation, before sending them to the API. While I do mention providing `system` (which is also the default if not provided), It's still a limitation to what can be provided. I have included a link to the documentation along with an image for such.