Visually distinguish between namespaced and non-namespaced resources

[nwmac]

Follow-on work from 2.6.4:

Add a badge next to cluster-level resources when a namespace is selected (+ tooltip), so that the user knows they are viewing a cluster-resource and that the namespace filter does not apply - see design from @lvuch

This should all be done with the changes to add top-level icons to the navigation and remove the 2nd-level nav icons.

[lvuch]

Adding same note from 5147: This fix should also include nav accessibility as noted here - https://github.com/rancher/dashboard/issues/4388

[nwmac]

check in with @nwmac before starting on this ticket

[catherineluse]

For comparison, the upstream Kubernetes dashboard handles it by showing a Namespaced tooltip when you hover over an item in the side nav.