Cluster navigation visual redesign

[edenhernandez-suse]

Related to:
#5287
#6067
#6321

We need to scope down this in order to understand the main problem we want to solve. They are:

• Cluster side navigation has visual issues.
• Items are marked as global or namespaced, but we're not communicating it properly.
• Namespace-filtered items are not clear enough.

Manuele started an approach to these issues, we can work from there; however, this requires a discussion about how to solve it in a way that could be incrementally developed.

Subtasks:

• EPIC: Define a color palette that works with the future plans #8697

[edenhernandez-suse]

Final design for both themes: