smoke-test centroids + graph overlay layer (#1189)

* add test labels

* prettier + add clcik return to clickOn()

* prettier + begin test

* finish label counting test

* add util to get coordinates of element

* add test id to labels

* add test to check overlay transform

* remove logs

* rename to match master

client/src/components/graph/overlays/centroidLabels.js

@@ -62,6 +62,8 @@ class CentroidLabels extends PureComponent {
           key={key}
           className="centroid-label"
           transform={`translate(${value[0]}, ${value[1]})`}
+          data-testclass="centroid-label"
+          data-testid={`${key}-centroid-label`}
         >
           <text
             transform={inverseTransform}