[Docs] Mention Kerberos authentication provider in the docs

[azasypkin]

In #36112 we introduced Kerberos authentication provider, but it's not mentioned in the Kibana documentation yet. We should mention how it can be enabled in Kibana and how it works internally (the part about access/refresh tokens):

xpack.security.authc.providers: [kerberos]

or

xpack.security.authc.providers: [kerberos, basic]

/cc @arisonl

[elasticmachine]

Pinging @elastic/kibana-security

[bizybot]

Adding a note here so we do not miss to update the stack-docs.
https://github.com/elastic/stack-docs/blob/master/docs/en/stack/security/authentication/kerberos-realm.asciidoc
We need to mention that Kibana supports Kerberos and a link directing to the Kibana docs for configuring authentication using Kerberos.

[tvernum]

Can we remove the

You cannot use the Kerberos realm to authenticate users in {kib}
part of the note now?

Why would we want to wait for the Kibana docs update, when we know the stack docs are wrong and confusing users?

[arisonl]

Hey folks, Kibana docs update coming very soon!