[FR] Add `source_updated_at` to Rule Schema as a Build Time Field

**Is your feature request related to a problem? Please describe.**
No.

**Describe the solution you'd like**
Add `creation_date` and `updated_date` to rule objects when a release package is created.

**Additional context**
When we build a rules release package, all rule objects should have a `creation_date` and `updated_date` field in them. This will be used by Kibana for the updates review workflow.

@jpdjere @approksiu

Dev branch: https://github.com/elastic/detection-rules/tree/fr-add-dates-to-rule-data