istio upgrade e2e tests using either helm or istioctl (#17945)
istio upgrade e2e tests using either helm or istioctl (#17945)

* istio upgrade e2e tests using either helm or istioctl

* add --yes flag for upgrade

* add todo comments

* restrict --install_options can only choose between helm and istioclt

* change --yes to --skip-confirmation

* update test_crossgrade

* address comments

smawson/istio,istio/istio,istio/istio,smawson/istio,smawson/istio,istio/istio,smawson/istio,istio/istio,istio/istio,smawson/istio,smawson/istio