Collect metrics while Prometheus scrape

[zlodes]

Now there are two ways to collect metrics:

1. Schedulable Collector: collect metrics every minute using Laravel Scheduler
2. Collect metrics on events: update metrics directly on any app action or event

It would be great to have an ability to collect metrics when the Prometheus is scrapping the target.

Warning
These Collectors MUST NOT use any external resources to update a metric to keep scrape time as less as it's possible!