The e2e suite covered the operator's in-process API server proxy but
not the ProxyGroup-based one. Add tests for both proxy modes that
drive a ConfigMap through its lifecycle via the proxy, verify a
forbidden request is rejected, and check that deleting the ProxyGroup
cleans up its StatefulSet and Tailscale Service.
Fixestailscale/corp#38009
Change-Id: Ifc0be47ce32dd96f8daa748af6785a8b82ec19a7
Signed-off-by: David Bond <davidsbond93@gmail.com>