Add edit function for imagepin widget

Hello!

There are a couple of things that needs to be addressed before going ahead with this issue:

- We are mixing two issues here: code from 3352443 🐛 Incompatibility with hook_event_dispatcher module Active is present in this patch. This should not be the case. We will need the issue to be fixed, but we can not add the same changes here. For that I'm creating a new patch and interdiff attached to this comment.

- The edit form should have a proper naming inside interface.
- Ajax functionality can not work for the entire wrapper of forms. Should work only for the selected form, and wrapper id can not be test, we should change it.
- The issue description is not complete. Please, we need to add more info to it.

Here is a new patch version with changes to not break pin positions when saving existing widgets changes.