Meta: #4117

Description

We need to create a new section within Elastic Security requirements, Entity analytics perquisites and requirements, which outlines the privileges users will need to enable the risk scoring detection engine.

Details are in the Google doc here. Also include the known limitations, which thus far are only applicable to 8.11.

Note: For 8.11, we'll publish the specs for ESS/classic docs, then will create separate spec docs for Serverless.