E2E: Advanced namespace/project filtering (with developer tools logic)

[gaktive]

System namespaces

• If you have enabled developer tools to allow see all namespaces, then these prefixed namespaces would appear. Similarly, without this enabled, these should remain hidden; no system project should appear.
• The UI should filter out all namespaces prefixed with c-, p- or local unless the developer tools are turned on in the user preferences. Note: These namespaces only exist in the local Rancher server cluster. Rancher uses them for managing RBAC. Namespaces in the System project should still be shown.

(originally from #6613)