Add a switch configuration option for Cron monitoring

[summerKK]

for #836

[cleptric]

You can set the DSN to null. It has the same effect. I'm not in favour of adding yet another option.

[summerKK]

You can set the DSN to null. It has the same effect. I'm not in favour of adding yet another option.

Sometimes may need the DSN locally for debugging, and then after a while you forget to clear the DSN to execute the schedule:run, and that's a tragedy!😭

[cleptric]

We'll add a new before_send_check_in option. This will allow you to conditional disable sending check-ins. getsentry/sentry-php#1690