[Internal]: Update docs to reflect deprecation of logs, metrics, and synthetics ILM policies

[Supplementing]

Description

The logs, metrics, and synthetics ILM policies have been deprecated for some time in favor of {name}@lifecycle (name in this case is either logs, metrics, or synthetics). Users should migrate to using these @lifecycle ILM policies moving forward. The note about this should probably live somewhere on this section of the docs: https://www.elastic.co/docs/manage-data/lifecycle/index-lifecycle-management/tutorial-customize-built-in-policies.

cc: @vishaangelova @juliaElastic

Resources

See the following issues and PR's for more context:

• https://github.com/elastic/ingest-dev/issues/5770
• https://github.com/elastic/sdh-beats/issues/5271
• [Discussion] Naming convention for builtin pipelines elasticsearch#96267

Also see this comment for a better explanation of when this applies and when the user will see the callout in Fleet that will direct to this documentation: elastic/kibana#243416 (comment)

Which documentation set does this change impact?

Elastic On-Prem and Cloud (all)

Feature differences

N/A

What release is this request related to?

9.2

Serverless release

Unknown, work is still ongoing around these changes. See https://github.com/elastic/ingest-dev/issues/5770

Collaboration model

The documentation team

Point of contact.

Main contact: Any of: @Supplementing @juliaElastic @kpollich

Stakeholders: @elastic/fleet