[Mesh] Replace Policies tab with Resources tab

[schogges]

Description

This new tab will include new resources such as

• Policies
• MeshIdentities
• MeshTrusts
• ...

Investigate how we can combine different resources in one view (filters?)

Investigate wether we can remove the legacy policies and what potentially makes it still able to use them.

[johncowen]

We have a name for the "Policy" group, but we should try and avoid naming the "non-Policy" group via UI. Like a "don't show policies" toggle.

We were talking about potential weirdness of having things like MeshService in two separate places.

[schogges]

I've created two sub-issues to be able to separately work on the linking from the generic resources routes to the respective resource detail pages. Until this is done we link to the generic resource detail view.