nixos: kubernetes fixes

* Fix reference CNI plugins
  * The plugins were split out of the upstream cni repo around version
    0.6.0

* Fix RBAC and DNS tests
  * Fix broken apiVersion fields
  * Change plugin linking to look in ${package}/bin rather than
    ${package.plugins}

* Initial work towards a working e2e test
  * Test still fails, but at least the expression evaluates now

Continues @srhb's work in #37199

Fixes #37199