This adds the v1 lease controller

This refactors the v1 lease controller. It makes two functional differences
to the lease controller:
* It no longer ties lease updates to node pings or node status updates
* There is no fallback mechanism to status updates

This also moves vk_envtest, allowing for future brown-box testing of the
lease controller with envtest

node/lease_controller_test.go

@@ -0,0 +1,13 @@
+package node
+
+import (
+	"errors"
+	"testing"
+
+	"gotest.tools/assert"
+)
+
+func TestNotReadyError(t *testing.T) {
+	n := newNodeNotReadyError(nil)
+	assert.Assert(t, errors.Is(n, &nodeNotReadyError{}))
+}