Display hotspots' secondary locations

Showing secondary locations in the security hotspots page. As part of the tasks we will:

• Extend the response of “api/hotspots/search” to include secondary locations data.
• Update WS description of api/sources/issues_snippet that it is used for hotspots too.
• Extend “api/hotspots/show” response to return secondary locations.
• Update the UI in the hotspots list box on the left side to show the file name, secondary locations, location markers, and the ability to collapse the markers.
• In the code snippets on the right side, update the UI to display secondary locations within the code snippet.
• Move code snippet into its own tab
• Initially, the code snippet tab should scroll to the primary location
• If the user clicks on the secondary location on the left hotspots box, UI will highlight the same in the code snippet on the right.
• Adding support to move through locations with the keyboard.