* Add context to "tsh ls" in docs
Fixes#7051
- Create a partial for how the Teleport Auth Service filters Nodes
based on user roles/logins in response to queries.
- Add the partial to provide context for example commands that include
"tsh ls".
- Make our existing text on Teleport's authorization checks clearer
by enumerating the checks in the order they are executed in
services.RoleSet.CheckAccess.
Note that this does not change guides that instruct the user to create
a new user and role, since a user following these guides will see the
correct "tsh ls" output.
* Respond to PR feedback
Joel