Use series name in tooltip

Previously the internal ID for an individual bar chart was used to
identify the series data in the tooltip.

This was confusing so now the series name is used to label the data
points in the tooltip.

src/plugins/profiling/public/components/chart-grid.tsx

@@ -37,7 +37,7 @@ export const ChartGrid: React.FC<ChartGridProps> = ({ maximum }) => {
       const uniqueID = `bar-chart-${i}`;
 
       const barchart = (
-        <BarChart id={uniqueID} name={uniqueID} height={200} data={subdata} x="x" y="y" />
+        <BarChart id={uniqueID} name={keys[i]} height={200} data={subdata} x="x" y="y" />
       );
 
       const title = (