Unify tooltip options across visualizations (#33892)

* Unify tooltip options across visualizations

* Update tests

* use addTooltipOptions in piechart

Co-authored-by: Oscar Kilhed <oscar.kilhed@grafana.com>

devenv/dev-dashboards/panel-graph/graph-ng-gradient-area.json

@@ -97,7 +97,7 @@
           "displayMode": "hidden",
           "placement": "bottom"
         },
-        "tooltipOptions": {
+        "tooltip": {
           "mode": "single"
         }
       },
@@ -186,7 +186,7 @@
           "displayMode": "hidden",
           "placement": "bottom"
         },
-        "tooltipOptions": {
+        "tooltip": {
           "mode": "single"
         }
       },
@@ -275,7 +275,7 @@
           "displayMode": "hidden",
           "placement": "bottom"
         },
-        "tooltipOptions": {
+        "tooltip": {
           "mode": "single"
         }
       },
@@ -363,7 +363,7 @@
           "displayMode": "hidden",
           "placement": "bottom"
         },
-        "tooltipOptions": {
+        "tooltip": {
           "mode": "single"
         }
       },
@@ -452,7 +452,7 @@
           "displayMode": "hidden",
           "placement": "bottom"
         },
-        "tooltipOptions": {
+        "tooltip": {
           "mode": "single"
         }
       },
@@ -541,7 +541,7 @@
           "displayMode": "hidden",
           "placement": "bottom"
         },
-        "tooltipOptions": {
+        "tooltip": {
           "mode": "single"
         }
       },