Expand enforced namespace filtering to multiple namespaces and projects

[richard-cox]

This uses a new endpoint that has yet to merge. See rancher/rancher#40140, rancher/rancher#41536 (merged, but not in v2.7-head yet) feature available in v2.7-head

Summary

Fixes #7618

Occurred changes and/or fixed issues

• Users can currently enable a performance feature to enforce filtering by a single namespace, and only fetch resources from within that namespace, when there are a lot of resources
• This feature expands on this to allow users to select projects, and multiple of each

Pertinent Points

• Incompatible with incremental loading / manual refresh
  • Harder to get counts (need to sum up from different namespaces)
  • Requires use of new steve pagination
• Enforced NS threshold has been removed
  • The threshold only applies to the primary resource. This has issues when loading a low count primary (daemon sets) which depends on a very high count secondary (pods)
  • Fixing this would involve knowing all secondary resources a list uses, which isn't currently possible (each resource is requested individually, need to know them all first)
• There is no way to subscribe to changes in multiple namespaces (it's either in one ns or all ns's)
  • We mock this in subscribe by sub'ing to all ns but only persisting changes to resources from within the target namespaces
• Everything should work with Advanced Worker enabled

Technical notes summary

Areas or cases that should be tested

• Enabling/Disabling the updated performance setting (only compatible ones should be enabled)
• All workloads list fetch the correct data (via http request)
  • New endpoint is hit for primary resource type, only resources from selected namespaces/projects are shown
  • New endpoint is hit for all secondary resource types
• All workloads list update with the correct data (via socket)
  • Changes to resources in the list are automatically shown (when changed via another context/browser/etc)
  • Changes to resource not in the list do not show (creating a new resource not in a selected namespace/project doesn't appear in the list)
• All of above but with the advanced worker enabled
• Creating resources works fine
  • Navigate to a create page of a resource (deployment, pod). Resource can be created, user is returned to the resource list and, if the resource was created in a namespace in the filter, the new resource should be shown
• Edit resources work fine
  • Navigate to an existing resource page (deployment, pod). Resource can be edited, user is returned to the resource list and the edited resource should be shown
• Both Upstream and Downstream clusters work correctly