[Docs] Provide best practices for using Spaces with RBAC

[legrego]

Following a discussion with @woodywalton regarding #100974, we came to the conclusion that we are lacking documentation for best practices when setting up Spaces with RBAC. Additionally, I think it would be great to call out known limitations, such as:

• Viewing index patterns that you don't have the privileges to use (Only list index patterns that a user has read access to #23294)
• Features that are not space-aware (such as Watcher)
• Features that require unique privilege configurations (such as many stack management apps)
• [others]

[elasticmachine]

Pinging @elastic/kibana-security (Team:Security)