istioctl x wait removed from 1.23; test update needed

[craigbox]

_wait_for_istio() is used throughout the doc tests, but relies on an experimental feature which has been removed in 1.23.

/tests/util/helpers.sh:

# Wait for Istio config to propagate
# usage: _wait_for_istio <kind> <namespace> <name>
_wait_for_istio() {
    local kind="$1"
    local namespace="$2"
    local name="$3"
    local start=$(date +%s)
    if ! istioctl experimental wait --for=distribution --timeout=10s "$kind" "$name.$namespace"; then
        echo "Failed distribution of $kind $name in namespace $namespace"
        istioctl ps
        echo "TEST: wait for failed, but continuing."
    fi
    echo "Duration: $(($(date +%s)-start)) seconds"
}