[Edge] Dropped support for `setActive` (used to focus editor in some cases).

[kkrzton]

The parent task is #14819.

The newest version of Edge browser (Edge 38.14393, EdgeHTML 14.14393) dropped support for setActive which ​is used to focus editor in some cases (e.g. divarea plugin) to ​prevent unwanted scrolling.

While focus should be probably used in this case, it causes this unwanted scrolling so some workaround should be also applied.

Steps to reproduce

1. Go to plugins/divarea/samples/divarea.html.
2. Run CKEDITOR.instances.editor1.editable().find('table').getItem(0).scrollIntoView() in the console.
3. Run CKEDITOR.instances.editor1.focus() in the console.

To check if editor was focused use document.activeElement.

Expected result

Editor should be focused without scrolling.

Actual result

Editor is focused and scrolled to the top.

Other details (browser, OS, CKEditor version, installed plugins)

Edge (Edge 38.14393, EdgeHTML 14.14393)

---

This issue causes some unit tests fails in:

• tests/core/config/inline
• tests/core/dom/documentfragment
• tests/core/editable/domfix2
• tests/core/editable/wysiwyg
• tests/core/editor/title
• tests/core/filter/editor
• tests/core/selection/editor
• tests/core/selection/fake
• tests/plugins/autoembed/autoembednotifications
• tests/plugins/floatingspace/floatingspace
• tests/plugins/image/image
• tests/plugins/mathjax/mathjax-mock
• tests/plugins/pastefromword/pastefromword
• tests/plugins/sourcearea/source
• tests/plugins/uploadimage/uploadimage
• tests/tickets/11500/1

At least using focus (instead of setActive) fixes the tests but scrolling problem remains.