Add doc for filter support for cli tools

[kimlisa]

Description

By 9.1 the cli tools tsh and tctl will have filter support. This PR adds docs on how to use the filters.

Rendered Doc Links

• new CLI flags
• predicate language page
• filter field section rbac sessions
• filter field section for impersonation

CLI help

The CLI --help has the following minimum instructions (same output for supported resources):

[kimlisa]

the predicate language is also used for access requests, but i could not find documentation on how to define the fields (so i left it out for now). there are mentions of the field here though but with no examples: https://goteleport.com/docs/setup/reference/terraform-provider/#teleport_role,

i'm not sure if these fields are only applicable to terraform provider?

[ptgott]

Thanks a lot for putting this together!

[ptgott]

Just left some minor suggestions

[ptgott]

I don't see list used literally within a configuration resource, so "the list" might not be the clearest description to use here. Is there another way to phrase this that might be more recognizable? In other words, where would a user know how to find the value to use here?

[kimlisa]

actually, the doc says that user traits typically come from an external identity provider, so this tells me this value will rarely change, so instead of <list name> i put the actual value of what it will typically be