Remove "Only Namespaced Resources" & "Only Cluster Resources" from namespace filter

[gaktive]

Upon discussion with @nwmac, "Only Namespaced Resources" & "Only Cluster Resources" have become irrelevant with our recent modifications to our navigation. They're also kinda unclear (the subtext is that Cluster Resources aren't in namespaces).

We should remove those two options from the namespace filter.

[richard-cox]

These two options are involved in lots of weird filtering, so would be good to remove them and that complexity. This issue should involve removing these two filter values.... and wherever they were used in code