📝 Summary

Currently the observability alerts and cases pages are hidden by default. Similarly, the alert index templates and indices are not created or updated and no alert documents are written on alert execution. The feature flags that control this should default to being enabled if we want this to be available to all users.

✔️ Acceptance criteria

• The feature flag xpack.ruleRegistry.write is set to true by default.
• The feature flags for the observability alerting and cases pages are set to true by default or removed.