Button to create a new epic from an epic

In an issue you can create an issue from a new issue, i.e.

This issue does the same for an epic.

There is a small difference, right now to create an epic, you go to the epic list page and you click the New epic button. But you do not go to a dedicated new epic web form. I think new object web forms are messy and a cost to maintain and not a good design for GitLab in general. We should encourage users to create objects quickly, and then interact with the existing already created object by editing it. We shouldn't encourage users to spend a lot of upfront time interacting with a new object web form before clicking submit. We want to push the experience for users to create the smallest thing, so that we users can immediately collaborate. This is what epics right now is better than issues at. So if we add the ability to create an epic from within an epic, we should do the same here, that button should open an inline dropdown (not a web form).