Managing access to machine learning Kibana Spaces

[lcawl]

Related to elastic/kibana#70487

The following documentation needs to be updated to reflect changes to machine learning feature controls in 7.9:

• Remove "UI only" privileges from machine learning APIs: [DOCS] Fix security links in machine learning APIs elasticsearch#60098
• Update list of privileges in https://www.elastic.co/guide/en/machine-learning/master/setup.html: [DOCS] Update machine learning security privileges #1304
• Update list of privileges in https://www.elastic.co/guide/en/kibana/master/xpack-ml.html: [DOCS] Remove list of privileges from ML overview kibana#77541
• Remove note about machine learning exception in https://www.elastic.co/guide/en/kibana/master/xpack-kibana-role-management.html: [DOCS] Update ML note in Kibana role management kibana#77538

The list of user (read) and admin (all) permissions in the code: https://github.com/elastic/kibana/blob/master/x-pack/plugins/ml/common/types/capabilities.ts