[App Services] Expand API to allow communication from plugins to the TopNavMenu

[Heenawter]

Describe the feature:

Right now, communication between the TopNavMenu and any plugins that use it is more-or-less in a single direction - specifically, the TopNavMenu communicates to the plugin and controls its inner state. However, as part of adding in-product help to Discover, it was discovered (:wink:) that there are certain use cases where the ability to trigger events in the TopNavMenu from within a plugin might be desired - for example, allowing a link inside of Discover to open the SuperDatePicker

Describe a specific use case for the feature:

Right now, the empty state of Discover has three suggestions for users to help them see their data:

Notice that the final suggestion (Try temporarily disabling filters.) has an action attached that will disable all filters - in order to improve the empty state, it would be awesome to attach actions to the other two suggestion, as well:

1. The action for the Try searching over a longer period of time. suggestion would open the SuperDatePicker.
2. The action for the Try searching for a different combination of terms. would open the query bar or maybe even clear it.

However, in order to do this properly, Discover would need to be able to trigger the appropriate onClick actions in TopNavMenu.

⭐ Click here for a PR that includes a demo of how this could improve Discover's empty state

[elasticmachine]

Pinging @elastic/kibana-app-services (Team:AppServicesSv)

[Dosant]

My first thought was to use forwardRef in the top bar component to expose imperative APIs, but then I thought maybe we should use uiActions plugin for this instead. This will allow anyone to trigger actions that will, for example, open a date picker

We need to figure out how to handle non compatible actions - for example - Discover shouldn't suggest to "extend time range" if data view without time field is selected because there will be now date picker shown. Our system also shouldn't allow executing "openDatePicker" action in this case and should be able to let consumers know about this.

[elasticmachine]

Pinging @elastic/kibana-vis-editors @elastic/kibana-vis-editors-external (Team:VisEditors)