Manage Elastic Defend section cleanup (#632)

- Cleans up the Solutions and use cases > Security > Manage Elastic
Defend section, and consolidates serverless/stateful content.
- Removes serverless raw migrated files.

Previews:

-
[Endpoints](https://docs-v3-preview.elastic.dev/elastic/docs-content/pull/632/solutions/security/manage-elastic-defend/endpoints)
-
[Policies](https://docs-v3-preview.elastic.dev/elastic/docs-content/pull/632/solutions/security/manage-elastic-defend/policies)
- [Trusted
applications](https://docs-v3-preview.elastic.dev/elastic/docs-content/pull/632/solutions/security/manage-elastic-defend/trusted-applications)
- [Event
filters](https://docs-v3-preview.elastic.dev/elastic/docs-content/pull/632/solutions/security/manage-elastic-defend/event-filters)
- [Host isolation
exceptions](https://docs-v3-preview.elastic.dev/elastic/docs-content/pull/632/solutions/security/manage-elastic-defend/host-isolation-exceptions)
-
[Blocklist](https://docs-v3-preview.elastic.dev/elastic/docs-content/pull/632/solutions/security/manage-elastic-defend/blocklist)

Author: natasha-moore-elastic