RFC: Add ability to configure session idle timeout

Describe the solution you'd like

• Currently UI has a local, browser based inactivity process where after a configurable amount of time we show a modal with a countdown. On reaching 0 the UI will close sockets and only allow the user to refresh the page to continue
• The concept of idle state will now be controlled via the backend and we need to update the above process with it
  • Remove the performance configuration section for the old inactivity process
    • For a minor release cycle (?) replace content with banner to indicate new process and location of settings
  • Add a new setting to handle updates to auth-user-session-idle-ttl-minutes
    • We need to make the description for it and auth-user-session-ttl-minutes crystal clear
      • auth-user-session-ttl-minutes - "Custom TTL (in minutes) on a user auth session. This is the maximum duration a session can stay alive regardless of user activity in a browser. This should be larger than auth-user-session-idle-ttl-minutes"
      • auth-user-session-idle-ttl-minutes - "Custom idle TTL (in minutes) on a user auth session. This is the maximum duration a session can stay alive when there is no user activity in a browser. This should be larger than auth-user-session-ttl-minutes"
  • When the user interacts with the UI they are classed as active and we update the backend
    • This should happen at log-in (when the session starts)
    • This should be debounced by the idle timeout (to avoid spam)
    • To update backend
      • Find token associated with current session
      • POST to a new endpoint /v1/cattle.io.ext.useractivity

        • {
            "apiVersion": "ext.cattle.io/v1",
            "kind": "UserActivity",
            "spec": {
              "tokenId": "token-xxxxx"
            }
          }
          

        • tokenId comes from the /v3/tokens resource associated with the current session
        • The response will contain the date + time the session is set to expire on
          • status.currentTimeout
  • We should track the current idle timeout time and when approaching it
    • When x (tdb) time away from the auth-user-session-idle-ttl-minutes we make a GET request to /v1/cattle.io.ext.useractivity to fetch the latest currentTimeout value.
    • If this has changed - we need to restart the process to trigger x time away from the new timeout date / time
    • If this is the same
      • stop watching for user interaction
      • show the idle modal with countdown
      • if user specifies they're here POST to /v1/cattle.io.ext.useractivity as per user activity and close modal
      • if no user action in theory we should just be able to refresh page and user taken to log in (needs confirming)

Additional context
SURE-2982

Dependent on rancher/rancher#45931