[Multiple Datasource] Allow to mount other top nav menu when mounting data source menu

[BionIT]

Is your feature request related to a problem? Please describe.
In #6082, we introduced a new component which takes advantage of setMountPoint exposed by MountPointPortal to mount it to the navigation bar - big thanks to @ashwin-pc for providing the suggestions. The problem we found is in the Maps plugin, it will override the TopNavMenu if there is any since it uses the same mount point.

Describe the solution you'd like
We should keep the TopNavMenu while mount the data source menu into the navigation bar, there are 2 options:

Option 1:

• use the data source menu to mount the components mounted via the topNavMenu by taking the logic from TopNavMenu https://github.com/opensearch-project/OpenSearch-Dashboards/blob/main/src/plugins/navigation/public/top_nav_menu/top_nav_menu.tsx#L92 into the data source component, while the draw back is TopNavMenu also renders search bar which is outside of the mount point. Thus data source menu will basically need to copy the code from topnavmenu

Option 2:

• use TopNavMenu as the top component for all data source components, and drawback is then it needs to expose properties that is only meaningful for data source components

Option 3:

• mount both topNavMenu and data source menu for Maps, and topNavMenu will still render the search bars, while data source menu will render the menu buttons to be mount by topNavMenu

Describe alternatives you've considered

Additional context

Add any other context or screenshots about the feature request here.

[ashwin-pc]

If they are already using the TopNavMenu component, then they can just add a new menu item to its config prop. the suggestion to use setMountPoint was for plugins that dont already use the TopNavMenu component :)

Ref: how discover does it https://github.com/ashwin-pc/OpenSearch-Dashboards/blob/16f1b35b971066c0f2f20d7bb01a2563c8da25dc/src/plugins/discover/public/application/view_components/canvas/top_nav.tsx#L85

[BionIT]

Based on discussion on 3/21/2024 with @ashwin-pc @Flyingliuhub @ZilongX @yujin-emma , we will add a boolean in TopNavMenu and a top level data source menu props in the TopNavMenu component to allow rendering data source menu together with top nav menu. This will allow Maps plugin that already uses top nav menu to mount both menu at the same navigation bar without overriding each other.