CRONS new monitor config options

### Problem Statement

See https://github.com/getsentry/team-sdks/issues/43

### Solution Brainstorm

Add new options:
- `failure_issue_threshold`: how many consecutive failures we should wait for to create an issue
- `recovery_threshold`: how many consecutive failures we should keep track to resolve an issue

Also document the new options on docs.sentry.io

