[Drilldowns] Embeddable context menu trigger

[Dosant]

Describe the feature:

Drilldowns will support picking triggers #59569

One possible new trigger is "Context menu trigger",
This will allow users to defined custom options in embeddable panels context menu.

• For url drilldown
  • will allow to navigate to external url and won't provide any event variables
• For dashboard drilldown
  • just won't extract any filters to pas to destination dashboard

Overall trigger<->drilldown schema would look something like this:

Originally suggested by @streamich during url drilldown discussions.

[elasticmachine]

Pinging @elastic/kibana-app-arch (Team:AppArch)