Improve top-level menu items behavior and appearance

[snasovich]

Setup

• Rancher version: 2.6.1
• Browser type & version: Chrome, latest

Detailed Description
Following up on #4358, it would be great to improve behavior/visuals for top-level menu items that are clickable and have content associated with them (e.g. "Cluster") vs. the ones that don't (e.g "RBAC").
Currently, by just looking at the UI there is no way to tell which top-level menu items fall in the first or the second category. Also, with top-level item with content selected, there is nothing on the UI that indicates that this item is actually selected. Compare how it looks like with "Cluster" selected vs. "Nodes" selected:
"Cluster":

"Nodes":

Context

Improvements in this area will make it more intuitive to use Rancher UI.

[catherineluse]

Should this be in v2.6.6 since it ties into #4431?

[edenhernandez-suse]

This issue is a bit outdated.

It would be great to improve behavior/visuals for top-level menu items that are clickable and have content associated with them (e.g. "Cluster") vs. the ones that don't (e.g "RBAC")

This was fixed at some point. Menu items without children don't show a chevron anymore.

Also, with top-level item with content selected, there is nothing on the UI that indicates that this item is actually selected.

This is also fixed: those items are now highlighted.

However, there is a bug with the Cluster section. It doesn't get the active CSS class and, therefore, it's not highlighted.

There is also some weird CSS in the children list items:

That margin is wrong (and deleting it doesn't change anything).

[edenhernandez-suse]

I do see a possible improvement in the behaviour of the menu.

Sections without a landing page (like Storage) could be distinguished from those with a landing (like Cluster). One option could be that they don't show a cursor: pointer and are not clickable, only the chevron is clickable and it would deploy the children items.

That way, just scanning with the mouse or tab key would inform the user if that category has a landing page or it's just a group.

[kwwii]

Closing this as everything works as expected now except the selected background color of top level menu items. Created a new bug for that issue here #7937