Support namespaced UX Server

[dseapy]

Summary

Currently if using Role/RoleBinding there are errors in the UX Server when trying to list namespaces. To support running the server without cluster-wide permissions, it would be good to add --namespaced and --managed-namespace flags similar to how the controller currently does.

Use Cases

User installing numaflow may not have sufficient permissions on their cluster to do a cluster-wide install. Alternatively one may want to run multiple instances of the server restricted to their namespaces.

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