Endpoint response actions section cleanup (#660)

- Cleans up the Solutions and use cases > Security > Endpoint response
actions section, and consolidates serverless/stateful content.
- Removes serverless raw migrated files.

Previews:

- [Endpoint response
actions](https://docs-v3-preview.elastic.dev/elastic/docs-content/pull/660/solutions/security/endpoint-response-actions)
- [Automated response
actions](https://docs-v3-preview.elastic.dev/elastic/docs-content/pull/660/solutions/security/endpoint-response-actions/automated-response-actions)
- [Isolate a
host](https://docs-v3-preview.elastic.dev/elastic/docs-content/pull/660/solutions/security/endpoint-response-actions/isolate-host)
- [Response actions
history](https://docs-v3-preview.elastic.dev/elastic/docs-content/pull/660/solutions/security/endpoint-response-actions/response-actions-history)
- [Third-party response
actions](https://docs-v3-preview.elastic.dev/elastic/docs-content/pull/660/solutions/security/endpoint-response-actions/third-party-response-actions)
- [Configure third-party response
actions](https://docs-v3-preview.elastic.dev/elastic/docs-content/pull/660/solutions/security/endpoint-response-actions/configure-third-party-response-actions)

Author: natasha-moore-elastic