[Request] Mark siem migrations APIs as deprecated

[vitaliidm]

Description

Mark siem migrations APIs as deprecated: https://www.elastic.co/guide/en/security/current/signals-migration-api.html

• Deprecate [POST /api/detection_engine/signals/migrations]
• Deprecate [DELETE /api/detection_engine/signals/migrations]
• Deprecate [POST /api/detection_engine/signals/finalize_migrations]
• Deprecate [GET /api/detection_engine/signals/migration_status]

Background & resources

• PRs: [Security Solution][Detection Engine] deprecates siem signals migration APIs kibana#202662
• Issues/metas: [Detection Engine][9.0] Deprecate legacy siem signals migration endpoints kibana#195523
• Point of contact: @vitaliidm
• Test environments:

Which documentation set does this change impact?

ESS only

ESS release

N/A

Serverless release

n/a

Feature differences

n/a

API docs impact

APIs should be marked as deprecated

Prerequisites, privileges, feature flags

No response