StateTimeline: Share cursor with rest of the panels (#41038)

* First working version of shared cursor for state timeline

* Only publish x value for time series

* Don't send legacy graph event

* Don't add y scale to cursor sync

* Snap cursor to the bottom of the canvas when sync is out of bounds

* Fix snapshot

packages/grafana-ui/src/components/GraphNG/__snapshots__/utils.test.ts.snap

@@ -95,7 +95,7 @@ Object {
       ],
       "scales": Array [
         "x",
-        "__fixed",
+        null,
       ],
     },
   },

packages/grafana-ui/src/components/TimeSeries/utils.ts

@@ -363,7 +363,8 @@ export const preparePlotConfigBuilder: UPlotConfigPrepFn<{ sync: DashboardCursor
         },
       },
       // ??? setSeries: syncMode === DashboardCursorSync.Tooltip,
-      scales: builder.scaleKeys,
+      //TODO: remove any once https://github.com/leeoniya/uPlot/pull/611 got merged or the typing is fixed
+      scales: [xScaleKey, null as any],
       match: [() => true, () => true],
     };
   }

packages/grafana-ui/src/components/uPlot/utils.ts

@@ -181,6 +181,11 @@ export function findMidPointYPosition(u: uPlot, idx: number) {
     y = u.valToPos((min || max)!, u.series[(sMaxIdx || sMinIdx)!].scale!);
   }
 
+  // if y is out of canvas bounds, snap it to the bottom
+  if (y !== undefined && y < 0) {
+    y = u.bbox.height / devicePixelRatio;
+  }
+
   return y;
 }