CKEditor is barely usable inside a bootstrap modal

Using CKEditor in a modal displays lots of various bugs related to the modal:

• macro menu is displayed behind the modal
• emoji menu is displayed behind the modal
• the different required user inputs are displayed also behind the modal (e.g. the attachment selector, the image selector, etc)

Note that in case of the image selector the recent refactoring (in 14.x) helped a lot as it now displays by default on top of the modal.
Except if that image selector is displayed once, and the modal with the editor is closed and reopened without creating back the editor. In such case, the image selector is also displayed behind the modal.

For testing the behaviours I'm mentioning easiest is to install Change Request 1.3, create a new change request and review it.