[BUG] Heatmap increase layers when zoom in/out

[junqiu-lei]

What is the bug?
When use heat map in OSD, user panned around zoomed in or out the same data points layer, the heatmap layer will increase to make data unreadable.

How can one reproduce the bug?
Steps to reproduce the behavior:

1. Sign in into Opensearch Dashboards
2. Navigate to the Dashboard option from the left pane
3. Select a dashboard that contains a heat map
4. Click on the heatmap
5. Right click on your browser and select Inspect
6. Coming back to the heatmap, select the + icon to zoom in
7. While zooming in, you can see additional layers of canvas being added from the Elements section that you opened in Step 5.
8. Additionally you are able to see that adding more layers leads to the heatmap blurring out.

What is the expected behavior?
Should be able to display only one data layer when zoom in/out on heatmap.

What is your host/environment?

• Browser: Google Chrome
• Version 1.3
• Plugins Heatmaps

Do you have any additional context?
Add any other context about the problem.

[ccgovuk]

To illustrate, these 3 screenshots are from the same map, same zoom level, just panned twice. Youll see each one has 3 more leaflet layers in the "leflet-pane leaflet-overlay-pane" div class.

[navneet1v]

@vamshin Please help in prioritizing the issue.

[vamshin]

This bug will be fixed part of Maps layers feature in 2.5
#15