When adding a new ClusterPermission, the cluster drop down shows all hub namespaces. This drop down should only show actual clusters. If a random namespace is chosen here, it causes issues in the next page namespace drop down selection as well. The cluster drop down is configured correctly on the EDIT page, so we can just copy the logic from there.

Create showing all namespaces:

Edit showing correctly, only real clusters:

This ticket will also be used for the following:

1. fix any type/eslint errors even if unrelated to the above issue
2. fix clear all X icon for user selection; it is not working and does not clear the user selections on create and edit pages